The Difference Between Moral Values and Moral Duties

Duty has to do with moral obligation with what I ought or ought not to do. But obviously, you're not morally obligated to do something just because it would be good for you to do it. Traditionally, our moral duties were thought to spring from God's commandments such as the Ten Commandments. On this foundation, we can affirm the objective rightness of love, generosity, self-sacrifice, and equality - but if there is no God, what basis remains for objective moral duties?