How does your confidence like? Is it like the dominoes lying side by side, with just one single touch on any of the pieces, all the others will collapse? Or is it like a strongly built concrete bridge that never minds the wind blows? I would wish that yours would be the second one. Never in a shaky state and never ever question your confidence. People are born with abilities, but are they born with confidence? Talking about confidence with abilities, I think it is built upon abilities. When a person grows up, along the way, they "realise" the abilities that they have. That they can draw amazingly well, they can sing very well and they are good with maths, and the confidence grows along as they keep on doing well.
When you think that it will be very good if there's a big boost in your confidence. I would like to say, just remember not to let it take over you, as it might have exceed certain level, inevitably leads to ego. You would not want it to become your enemy, where people feel irritated by your ego, initiated by your "top of the world" confidence, right? Confidence should be helping you to perform well, become the energy that drives you towards your goal, but never ever should be turned into the master of ego.
I believe that the confidence relies strongly on a person's persistence and determination. Imagine somebody who does so well in something whereby he gain the confidence as he goes. And then one day, he fails in doing things which he has so much confidence in. The confidence level may plunge to zero just like that, and he feels so despair. But someone with strong persistency will still remain his confidence level and continue doing it with full confidence, never mind the fails. If it happens, don't worry, cause you have your determination and abilities - your driving forces. Renew the confidence right away, refresh yourself, and keep on moving, cause it's not the end yet!