The greatest happiness comes with the most complete possession of one's faculties. It is in the moments when the mind is most active and the fewest things are forgotten that the most intense joys are experienced. This indeed is one of the best touchstones of happiness. The happiness that requires intoxication of no matter what sort is a spurious and unsatisfying kind. The happiness that is genuinely satisfying is accompanied by the fullest exercise of our faculties, and the fullest realization of the world in which we live.
~ Bertrand Russell, The Conquest of Happiness