Susanna Tamaro, Follow Your Heart

"Unshed tears leave a deposit on your heart. Eventually they form a crust around it and paralyze it, the way mineral deposits paralyze a washing machine."

"... but happiness is to joy as an electric light bulb is to the sun. Happiness always has an object, you're happy because of something, it's a condition whose existence depends on external things. Joy, on the other hand, has no object. It seizes you for no apparent reason, it's like the sun, its burning is fueled by its own heart."