"Every habit and faculty is maintained and increased by the corresponding actions: the habit of walking by walking, the habit of running by running. If you would be a good reader, read; if a writer, write. But when you shall not have read thirty days in succession, but have done something else, you will know the consequence. In the same way, if you shall have lain down ten days, get up and attempt to make a long walk, and you will see how your legs are weakened. Generally, then, if you would make anything a habit, do it; if you would not make it a habit, do not do it, but accustom yourself to do something else in place of it.

Discourses II.18 trans. Long