Happiness is neither virtue nor pleasure nor this thing nor that but simply growth, We are happy when we are growing. – William Butler Yeats

With penetrating insight, the mystics will tell us that when we have a desire for a certain thing, a certain experience, and we fulfill that desire, the happiness we feel is not something given by that thing or experience; it is due to having no craving for a little while. – Eknath Easwaran, The Mantram Handbook

Its obvious, but perhaps worth saying, that happiness has virtually nothing to do with the state of your intellect. – Daniel Keys Moran