I agree with this in principle. I think it instructive to point out that most (all) of us have our dark sides. (by that, I don't mean seriel killer impulses...) I mean, things we like, desires, fantasies, etc, that we really don't want out in the open to one degree or another.
Not that this is what you were referring to. But we are all a work in process, and the only way to grow is to experience things, events, and emotions. Including the selfish, immature ones. For most people, its like burning your hand on the stove, and you tell yourself, "I sure as hell won't do THAT again."
THAT could be that one night stand, drunken binge where you were your most charming, the time that you felt speaking out would be just the thing to show how smart you were, and it didn't, etc.
So you do have to fake it till you make it once you leave. I call it, trying things on. Sometimes, to learn about yourself, you have to stretch outside of your comfort zone. Otherwise, you will always be asking "What if....?"