Some of the hows, because who doesn't like a numbered list? (Don't answer that.)
1. They make me seem more cool and/or awesome.
2. They make people like me more.
3. They make my superiors think I'm more cool and/or awesome, and therefore like me more, and therefore I am more successful.
4. It would be super-awkward not to do the good thing. (An example: I'm going somewhere with friends, and I'm the only one with a car, and all of a sudden the question "Wait, how are we getting there?" drops into the conversation like a stone thrown into a still pond, and nobody looks at me, but I know they're all thinking at me, so I offer.)
5. I have an image to maintain, a helpful, good-thing-doing image, and it's getting kind of rusty and disrepaired.
6. I feel sorry for someone, so in order to stop feeling sorry for them I do a good thing for them. It seems like it's altruism, but it's actually just selfish, because I'm doing it to make myself feel better.
See? Not really good. These all help Ian the Pontificator.
But today...today I did something good, and I can't tell anyone what it was, or it'll stop being good.
"Why?" you ask in an inexplicable Polish accent.
"Because, dear Olaf, the only real reason I'd tell you would be to make me look better, and that would just be a strange sad mess of failure," I reply.
If I say what I did, and if I spread it around, it won't be a good thing any more. Which is indeed bothersome.
More bothersome, though, is the thought that perhaps even this blog post, vague though it be, divests my good thing of goodness. That would be an unhappy birthday.
Long live sneaky goodness.