Humans should take their happiness as seriously as they take themselves.
Fr. Alfred Delp, S.J. (+1945):
In order to be capable of leading a full life a person must stand in a certain relationship to God and obey certain rules. And the capacity for true happiness is also dependent on certain conditions of human life, on a serious attitude toward God. Where life does not unfold in communion with God it becomes gray and sordid, calculating, and joyless. Humans should take their happiness as seriously as they take themselves. And they ought to believe God and their own hearts when, even in distress and trouble, they have an intuitive feeling that they were created for happiness.