Pleasure is the happiness of fools.

Happiness is the pleasure of the wise.

~ Jules d'Aurevilly

True happiness is the unrestricted use of the mind.

~ Aristotle

Our own happiness always looks smaller than that of others;

our own misfortune always looks bigger than that of others.

~ Jean de Boisson

Those who can't enjoy happiness when it comes, shouldn't complain when it leaves.

~ Miguel de Cervantes

(I really like this one)