Jill, of all the nonsense that twists the world, the concept of 'altruism' is the worst. People do what they want to do, every time. If it sometimes pains them to make a choice - if the choice turns out to look like a 'noble sacrifice' - you can be sure that it is in no wise nobler than the discomfort caused by greediness . . . the unpleasant necessity of having to decide between two things both of which you would like to do when you can't do both. The ordinary bloke suffers that discomfort every day, every time he makes a choice between spending a buck on beer or tucking it away for his kids, between getting up when he's tired or spending the day in his warm bed and losing his job. No matter which he does he always chooses what seems to hurt least or pleasures most. The average chump spends his life harried by these small decisions. But the utter scoundrel and the perfect saint merely make the same choices on a larger scale. They still pick what pleases them.

Robert A. Heinlein