The pleasures of love are for those who are hopelessly addicted to another living creature. The reasons for such addiction are so many that I suspect they are never the same in any two cases. It includes passion but does not survive by passion; it has its whiffs of the agreeable vertigo of young love, but it is stable more often than dizzy; it is a growing, changing thing, and it is tactful enough to give the addicted parties occasional rests from strong and exhausting feeling of any kind.

The Pleasures of Love (1961).