Good deed for the day

I gave blood yesterday. It was not my first attempt, but it was my first time that I actually made a successful donation (no I didn't faint the first time, it was just that my vein in my left arm is not very suitable, so it was just painful, caused bruising and not much came out).

I was chatting to a lovely old man afterwards who had donated 95 times. We were talking about our motivation for donating, and this brought us onto a conversation about whether altruism really exists (or do we just do good things because it makes us feel good?). Discuss...