You should try to do more good in the world because it’s the right thing to do.
Unfortunately, this isn’t always sufficient motivation for people to act accordingly, so altruists often tell non-altruists about the personal benefits of altruism — the evidence that giving makes you happier, the friendly and supportive communities of altruists you can join, the sense of meaning altruism can bring to fill the void left by an increasingly secular world, and so on.
But leading an altruistic life is not always plain sailing, and I think it’s important to acknowledge that from time to time. And not only to acknowledge that times get rough, but the specific ways in which they get rough.-Holly Morgan, It’s Supposed To Feel Like This: 8 emotional challenges of altruism
Update: An additional useful link about a related topic, scrupulosity