It's ruinous for the soul to be anxious about the future and miserable in advance of misery, engulfed by anxiety that the things it desires might remain its own until the very end. For such a soul will never be at rest — longing for things to come it will lose the ability to enjoy the present things.

— Seneca, Moral Letters, 98.5b-6a (resource) Ryan Holiday, The Daily Stoic