Mentality is an interesting thing too much confidence and you are likely to fail, to little and you will too. Getting the right balance of what you know and what you are capable of is crucial to success in anything; whether it’s taking an exam, meeting a project deadline or starting up a new business.
If you approach something with the attitude of “i dont know how to do this, it’s way over my head, im never going to get this done”, chances are you won’t. If you dont know how to do something, you find out how. Most things are possible and where there’s a will, there’s usually a way.
I first got into PHP programming this way, i knew very little about PHP and was asked to make an ecommerce site for a client. I didnt know how to do it, but i knew it was possible as many other programmers (more competant at the time in PHP than myself) had already done it. So i accepted the project, researched it thoroughly and came up with a solution that my client was more than happy with, i learnt a lot during this project it was a huge stepping stone in PHP programming that helped me get to where i am now, plus i got paid to do it!
With success comes the chance of failure, both are good, so long as you learn from failure and confirm with success.