Though your genes might be selfish, your brain isn't.
Social psychologist Elizabeth Dunn of the University of British Columbia (UBC) in Vancouver, Canada, performed a series of studies on, admittedly, small groups to determine what contributes more to happiness: giving money away or spending it on yourself. She gave people money, told them to either donate it or splurge with it, and then quantified happiness levels.
In the spirit of Christmas cheer (even though this is Easter weekend,) either donating the money to charity or buying a gift for others produced more happiness than keeping it or spending it on oneself.
This empirically tested and quantified altruism is a lovely addition to the study of ethics. The studies should be replicated with larger sample sizes, but they are worth reading.
To give is not divine. It's neurologically motivated and behaviorally reinforced.