Reasonable Doubts?

I imagine other triathletes are more sure of themselves than I am. 

I have very little faith in myself. Or my abilities. I never think I am enough. That I've done as well as I could. That I trained enough. That I ate right. That my heart is in the right place. Hell, I even question if I should be even TRYING to do the things I try to do. 

Are those reasonable doubts? If they are or they aren't, they haunt me. 

Constantly.