No one who has seen a baby sinking back satiated from the breast and falling asleep with flushed cheeks and a blissful smile can escape the reflection that this picture persists as a prototype of the expression of sexual satisfaction in later life. – Sigmund Freud
What we call happiness in the strictest sense comes from the (preferably sudden) satisfaction of needs which have been dammed up to a high degree. – Sigmund Freud