Do you often find yourself wanting to do something, but never having the courage to just do it? Are you tired of feeling too weak to do even the most basic things? Does it seem that something always stops you from doing what you want, or you're always waiting for someone or something to give you a "push" before you act? Being too passive might be preventing you from taking life in the direction you'd like to see it go. Here are some ways to overcome passivity and make your own way in the world.
Understand why you tend to act passive. Passivity has various causes: lack of willpower, lack of hope, lack of encouragement from other people, negativism, laziness, lack of necessary means. Think about the way you tend to act when you're about to do something. If there's something that stops you from performing that action, think about the first thought that comes to your mind. Notice the subtle differences between these causes. Beware; sometimes these causes are combined. The more situations you find yourself in, the harder it is for you to do something.
If you think "I know I can't do it, so there's no point in trying in the first place", then you lack willpower. You just can't gather enough will to do it, even if you're actually able to do that thing.
If you think "It doesn't work. It never does; it probably won't work now either", you lack hope. You think that just because you couldn't do something in the past, you can't do it in the present either, forgetting that you've gathered more experience by now and that you can't predict whether something works or doesn't work; you're the one that makes it happen.
If you think "I can't do it by myself, and there's nobody there to support me", then you don't receive enough encouragement from other people. You feel you're not able to do something without getting help from others.
If you think "It won't end up well. I'd rather not change anything that risk to turn out that the change is for the worse.", then you are being negative. You build up scenarios in your head, convincing yourself that if something bad can happen, it surely will. You always think that no matter how good an action is in itself, the consequences are always bad.
If you think "I can't do it because doing that thing requires having something that I don't have", you lack the necessary means to do it. It can be an objective point of view... or not. Some people truly lack the means to do something, but others just aren't willing to work to achieve it. And here we go to the next reason...
If you think "It requires too much effort... and for what? It's not worth all the effort. Things will turn out well anyway", you are just too lazy to do it! You strongly believe in destiny and think that, if something is meant to happen, it will; regardless of what you do to achieve it.
Gain willpower. Willpower is that ability to control your thoughts and actions in order to achieve what you want to do; in other words, the ability to go for your dreams and do what you really want to. You can gain it by following your impulses and being spontaneous. Willpower is an ability you gain only by practicing; the more you practice it, the more you enjoy it and find reasons to practice it further.

Choose "Now or Never" as your motto from now on. Convince yourself to do something right when it occurs to you, and imagine that otherwise something bad will happen. It's very effective in gaining more courage to do things.
Start by achieving short term goals, like convincing yourself to do the laundry today and not waiting until tomorrow or studying for 15 minutes for an important test. After you'll be able to accomplish these little things, you can move on to something bigger, like moving to a place you've always dreamed to live in, or losing those 20 pounds that keep you from having the perfect body, or whatever big dreams you may have.
Gain hope. Stop convincing yourself you can't do something before trying; you can never know how things will turn out. Try some little, but very useful mental exercises: when you know there are high chances of something to happen, wish for it. When it will happen, you'll feel better just for knowing that you were right. It may sound stupid, but it's very useful in gaining more hope. Practice this often; it increases your expectations that something will happen, and therefore improves your hope.
Get motivated. You have willpower, you have hope- now all you need is a reason to do something. Think about your greatest wishes and picture having them fulfilled. Set some goals you want to achieve, and focus on achieving them. Constantly aiming somewhere sustains your motivation.
Set some reasonable goals and some rewards and auto-punishments for them too. Reward yourself if you eventually accomplish the goal, and "punish" yourself if you don't. Set a time limit if you must. For example, if you finish your homework before 18:00, you reward yourself a chocolate bar, and if you don't, no TV for you this evening. This makes you feel more motivated to achieve your goal, whether it's due to thinking about the delight of the reward or the fear of punishment.
Ask for help if you need to. Sometimes it feels better just to have somebody who understands and supports you, and you feel like you could do more. There must be someone that's close to you and you can trust; speak to them about your wishes and expectations and tell them you want them there for you. Even if the person can't do much to help you, just knowing you're not alone makes you feel better. Tell them what kind of support you need, if you have to; some people won't understand that just because you talk to them about something you want actual, not just moral support from them.
Be more positive. Stop worrying so much about everything and thinking that things won't end up well. Unless the whole Universe is conspiring against you (and it isn't), positive actions will more often than not have positive results, too. You may not be the luckiest person around, but there are ways to improve your luck.

Stop living your life according to Murphy's law. If you truly believe something bad is going to happen, it may happen more often than usually. In fact, it will only seem like that, because counting every little bad thing that happens to you and ignoring the good moments will lead you to think your life is rather unfortunate. Actually, people have about the same percentage of success and lack of success in their lives. There are no people that are luckier than others; just people who are better at organizing their lives and influencing their fate. If something bad can happen, it has a chance to happen and a chance not to happen; it doesn't always happen.
Understand what you need in order to do something, and try to acquire it. Don't shoot for the stars; for example, don't dream about being the best basketball player ever if you're short or making more money than Bill Gates if you're dirt poor. Be realistic in your expectations. If you don't have the means to do something, but they're still achievable, don't hesitate and start working to acquire them.
Get off your lazy butt. That's pretty obvious; being a couch potato won't get you anywhere. Any action requires a minimum effort; even for walking you need to move your damned legs- nothing can be done without effort. Of course, it's easier to accept everything right as it comes rather than make an effort to influence it. But persisting in this mentality can lead your life in the wrong direction. Don't be surprised if after 10 years you'll end up broke, buried in debts, single/divorced, and having to sell your precious TV to pay the bills- all this because you didn't move a finger to improve your life! Don't leave your whole life in fate's hands; realize that all the people that are renowned for something they had done in their lives didn't have it all from the very beginning- any brilliant politician, for example, had to climb up to the top; they weren't born already elected, you know.
Be confident. You need to believe in yourself in order to achieve what you want. Don't think too low of yourself; every human being is good at something. Make a list with all the things you achieved in the past. They don't have to be impressive CVs; even a small activity like washing the dishes counts.
Get to know the positive side of change. Change makes our life less boring, allows us to experience new things, makes us understand different lifestyles and different points of view, gets us out of trouble and refreshes us, making us lively and energetic. Once you get to enjoy one major change in your life, you will be tempted to make other changes.
Become more disciplined. If you're disciplined, you have lower chances not to be able to do what you want/have to. If you can't convince yourself to do something, it would be useful for you to be forced to do it by external circumstances.

Sign up for something. Anything. Knowing that you just have to be somewhere at some hour forces you to become more disciplined in your schedule. Passive people often don't do things right at the time they should be doing them; they usually put them off.
Ask a member of the household to constantly remind you to do some regular activities. You have to be warned by now; it's very annoying. But that's precisely the point; you'll start doing those things just to avoid being pestered by that person.
Join the Army if you think you can handle it. It's the most disciplinary thing anyone can do.
Never think you can't do something (unless, of course, nobody has ever done it before you and there's no certainty you can do it). Be strong, bold, assertive and persistent in your tries.
Make your life less boring. If you have no life, it's understandable why you act passive; anyone who is so bored with their own life lacks enthusiasm and livelihood. Try spicing up your life a little; get a new social life, go out more often, try a new hobby.