I think it may just be the uncertainty of how hard u are working. I know when I do intense therapy, I often go through confidence crisises. I am not sure why. But i think it may have someone to do with the idea that your wrapping your brain around all of the things, u aren't used to th level of comfortableness with all the things that used to not be comfortable, and u almost feel like its too good to be true. So u start questioning and doubting. Which is one of the worst thing unfortunately.