Melancholy

Melancholy may enter your soul, and ambush your happiness; but it will prepare you for true joy. Melancholy drives out all other emotions and feelings, so the source of all goodness may occupy the whole house. It shakes the yellow leaves from the tree, allowing fresh leaves to grow. It pulls up old bodily pleasures by the roots, allowing divine spiritual pleasures to be planted. Melancholy takes many things from the soul, in order to bring better things in return.

-Rumi, "Masnavi"