You bring up a good point... I think what you describe is attributable to fear of failure, or perhaps even just failed expectations. That is, the more effort you put into something there is some expectation of success to follow. When that doesn't match up to expectations... if you already have a fragile self-esteem or had self-doubt going into whatever venture, you just feel it all the more.

Of course the issue is success isn't a linear thing, it has peaks and valleys, but its sometimes hard to rationalize this as you're actually going thru it - you really just have to push going through those feeling like a loser phases.