This works for other things, too. If you're constantly evaluating whether breaking the rules is likely to pay off this time, you're probably going to break the

This works for other things, too. If you're constantly evaluating whether breaking the rules is likely to pay off this time, you're probably going to break the rules too much, or spend too much time processing about it. Deciding on a set of morals you will not break (except in extremis) frees your time and energy to do things that will pay off, at very little opportunity cost. Further, if you communicate that you've done this, either explicitly by discussion or implicitly by refusing to do things "just this once" that are wrong according to the rules you chose, you'll lower the transaction costs of others interacting with you, and thereby people will trust you and interact with you more. This is called "rep", I think. :)