Edith Wharton 
A Backward Glance [EPUB ebook] 

Years ago I said to myself: 'There’s no such thing as old age; there is only sorrow.’
I have learned with the passing of time that this, though true, is not the whole truth. The other producer of old age is habit: the deathly process of doing the same thing in the same way at the same hour day after day, first from carelessness, then from inclination, at last from cowardice or inertia. Luckily the inconsequent life is not the only alternative; for caprice is as ruinous as routine. Habit is necessary; it is the habit of having habits, of turning a trail into a rut, that must be incessantly fought against if one is to remain alive.