Happiness does not consist in amusement. In fact, it would be strange if our end were amusement, and if we were to labor and suffer hardships all our life long merely to amuse ourselves.... The happy life is regarded as a life in conformity with virtue. It is a life which involves effort and is not spent in amusement.
Modern science has as its object as little pain as possible, as long a life as possible - hence a sort of eternal blessedness, but of a very limited kind in comparison with the promises of religion.
People change, but there really are limits. One thing you discover in psychoanalytic treatment is the limits of what you can change about yourself or your life. We are children for a very long time.