What is Morality?

Some people believe in absolute morality, where some deity decided what is and isn't moral and that will never change. Others believe in relative morality, where what is moral for one person is not moral for others.

Since some murderers and war criminals do not believe that they did anything wrong, I have a hard time believing in absolute morality. That leaves me with relative morality, and the question I've been trying to answer, "How do I know if I am doing something wrong?" I don't believe in any particular deity, nor do I have strong faith in any particular book or group of people, so I must do what most people do and listen to my conscience. When I feel guilty, I try to change things so that I no longer feel guilty (example: If I insult someone without meaning to, I want to make sure to apologize to the person and make him understand that I regret what I said).

Let me take a step back. How can I decide is what someone else is doing is right or wrong? Simply put, If a person feels guilty, then that person is doing something wrong. That almost covers it, but that simple rule lets people kill each other as long as they feel no remorse. So there is an addition to the above rule, which is, If a person causes damage, then that person is doing something wrong. And combined it makes the simple rule of morality:
A person is doing something wrong when that person feels guilty or causes damage to another.

Now I'm sure that there are some holes in the above theory, but in general I think it works. It removes the idea of "victimless crimes" and hopefully will let people live and let live. If I want to have sex with two other men while smoking pot and cutting off my left leg, I should be legally allowed to (assuming that the other men consent).