I stumbled upon an article from the Washington Post called "If It Feels Good To Be Good, It Might Be Only Natural." The article explains that researchers at the National Institutes of Health have been conducting tests in an effort to determine whether or not altruistic behavior has a positive response hard-wired into the brain. The article states that when volunteers were asked to think of scenarios involving either donating or keeping a large sum of money, those who thought of acting out of compassion showed increased activity in the primitive part of the brain that lights up in response to food or sex (or drugs, in the brain of an addict). The study suggsests that the suppression of base and selfish urges is hard-wired into the brain to give us a feeling of pleasure.
So, my fellow codependents, we're not really saints. We're altruism junkies.