My confidence in most areas tend to come and go depending on the situation. It really sucks because sometimes I have no idea why my confidence fluctuates (so, no control over it).
However, one thing I've always had and always will have confidence in is my potential. Growing up I was put in gifted classes and was always told that I was a smart kid, so that's where it began. What bolstered that confidence is the fact that there has never been a time where I've truly invested myself in something and failed at it.