This is Seneca's 72nd letter to Lucilius, entitled on business as the enemy of philosophy. The subject concerning which you questioned me was once clear in my mind and required no thought. But I have not tested my memory of it for some time, and therefore, it does not readily come back to me. My mind needs to be unrolled, and whatever has been stored away there ought to be examined from time to time so that it may be ready for use when occasion demands.