This'll be my last post here man, but seriously, just don't over think things.
Whatever you do, shit WILL happen. But good things will too. You can be the evilest bastard in all the world, and some good will result from your actions. But the same goes for the most well intentioned of people.

Your best is all you can give. You give a damn, and that's the main thing. You'll most likely do more good than bad, so don't sweat it.