What does it mean?
Getting more things won't make you happy for long. Being grateful for what you already have will.
Who said it?
Hyman Schachtel: American rabbi and author (1907–1990). Source: The Real Enjoyment of Living (1954).
Happiness– Hyman Schachtel, The Real Enjoyment of Living (1954)
“Happiness is not having what you want. It is wanting what you have.”