I've been pondering myself (the subject that depresses me almost as much as everything else), and I think I figured out the reason I can't just lose myself to whatever form of debauchery or mindless hedonism that floats other peoples' boats:

I have a 'noble' heart.

That is to say, I possess a mind/personality that is not entirely pure, but desperately craves some more meaningful concept than doing all I want without giving a shit.

I am not an optimist, far from it, but I do wish I was.