We've all felt guilty at some point it seems, but have you ever stopped to wonder why we feel this emotion? What role does guilt serve? How did guilt evolve? Other animals don't seem to experience guilt as far as we know, so why humans?
Well, I think guilt is necessary for society to function, and there are different theories of how guilt works as a kind of social glue. One is that guilt is a sort of self-imposed punishment. When you do something wrong like hurting someone or lying, guilt kicks in and makes you feel bad so that maybe you won't do it again. Or, maybe guilt also makes you not only feel bad, but also gives you incentive to try to actually be a better person in the future.
In fact, research suggests that guilt does both of those things at the same time; it helps you recognize and feel bad about improper behavior and then spurs you to reach out to others and make amends.
In this way guilt is vital for a peaceful society. Without guilt there's less incentive to get along with other people, so you can imagine that a guiltless society would be pretty chaotic.