In the way of virtue, there is no standing still; anyone who does not daily advance, loses ground. To remain at a standstill is impossible; he that gains not, loses; he that ascends not, descends. If one does not ascend the ladder, one must descend; if one does not conquer, one will be conquered.

— St. Bonaventure (1221-1274).

(This is one of several quotes I have from an old email list. I do not know the original source.)