Far too often have i seen coworkers, friends or just people that i sorta know doubt themselves for no good reason whatsoever. Far too often have i seen this lead to missed opportunities, increased frustration and an ever decreasing amount of self confidence. For no good reason whatsoever. Each and every one of those people is capable of more than they give themselves credit for, yet very few of them would agree with me on that. And it is just such a waste. It's a waste of energy, time and talent/capabilities.
Me being the person that i am, i can't avoid sharing my opinion on this with them. And more than a few of them have said something along the lines of "that's easy for you to say, things just happen for you and you often just get your way". Well, i certainly don't get my way 100% of the time, nor would i want to because it would take away too many learning opportunities. But there is some truth to what they say because things indeed go 'my way' often enough. You wanna know why? Because i have a strong belief in myself. And when people talk to me, they generally realize that i'm indeed confident in my abilities instead of being perceived as insecure (note: it certainly isn't something i was born with, i had to 'cultivate' it)
And that, truly, is what you need to achieve for yourself. You simply can't expect anyone to believe in you if you don't even believe in yourself. You need to realize that you are capable of more than you give yourself credit for. You need to believe that you can improve and that there is more to you than what you're currently doing. You need to believe that there is no reason whatsoever that you should doubt yourself. Now, that doesn't mean that you should think the world of yourself or that you can do anything. That would in fact be highly counterproductive.
There are two things that you need to achieve something: one is hard work, and the other is confidence. You'll never get anywhere with hard work if you're not confident. And you'll never get anywhere if you're confident without putting in the hard work that really is required. Combine hard work with confidence however, and you will almost surely be rewarded for it in some way, sooner or later. It is however very important to remember that you should never be (or appear to be) over-confident. In fact, i've experienced on quite a few occasions that it actually helps tremendously to be completely honest about your shortcomings or any mistakes that you've made. If 'important' people ask you a question that you can't answer, don't bullshit them. Instead, simply say "you know, i have no idea... i'd have to look into that before i could make any statements on that". A lot of people are afraid to say that, but trust me, people will respect you for it. And if they don't, well, in the long term they're not worth trying to impress anyway.
Also, don't be afraid to talk about your shortcomings or faults. Everyone makes mistakes, everyone has issues, and everyone has flaws. Pretending not to have any of those will only result in people not believing you in general. Allow me to demonstrate this with an example. I'm gonna mention something about myself that quite a lot of you will laugh at. And even though there's going to be about 3000 people reading this, it really doesn't bother me to talk about this. Ready? Here it is: i utterly suck at parking cars. Yes, i'm male. Yes, i know we're supposed to be good at that. And yes, i know many people think it's embarrassing not to be able to properly park a car. And you know what? I truly couldn't care less whether or not that made you think less of me as a person, or a developer who's blog you happen to be reading, or even worse, are subscribed to. Because i know that it doesn't define me as a person. If anyone were to think less of me because i can't properly park a car, i'd take that as a big warning sign that that person probably has a shitload of insecurities himself and he's not quite being honest with himself. You've got issues as well and you've definitely got stuff that you're not good at either. Do yourself a favor: learn to accept it and be happy with what you can do.
And it really is as simple as that. Believe in yourself. Work hard. Be honest about your mistakes and your shortcomings. If you don't get any opportunities despite that, then you're wasting time on the wrong people, trust me (it's a lesson i very recently learned all too well). Build up your confidence. Go out and score with a hot chick (or guy if that's what you want), run a marathon, build some cool software, or do whatever else it takes for you to build up your self esteem. Seriously. Once you truly start to believe in yourself, you'll be amazed at how much easier life becomes. It's still not gonna be perfect, but well, at least you're gonna do a lot better than you used to. Quite frankly, there is no reason whatsoever to doubt yourself or your capabilities. You simply need to go out there and maximize those capabilities. And if you fail, as we all do from time to time, learn from it and come back stronger. That's really all there is to it.