Agree with the wise and wonderful people above.. I'd say pain... money changes people but the changes are slow and gradual I think and not guaranteed.. There are are some who would not change and may become more generous and giving as a result of money.. look at history and the philanthropists.
Pain is faster and more pervasive I feel... it's a quick thing... people become mistrustful, careful, cautious, suspicious, withdrawn or any number of other things and those changes tend to be more long lasting and hard to overcome