That's a very natural thing. When I was young, I thought I was pretty close to invincible and like every kid, thought I knew everything. Saddlebag is spot on with "the more I know, the more I realize how little I know." I think that's pretty fair saying to go with just about any venture in life.
With horses, there is never ending knowledge to be gained. When one stops seeking knowledge and feels they don't need it, that's when you get stale. I've been on a horse (multiple horses usually) on an almost daily basis for 25 years, I don't plan to stop learning until my body tells me I can't.
Life is like a camera. Focus on what's important, Capture the good times, Develop from the negatives and if things don't work out, Take another shot.