This, from the Nicomachean Ethics:
It is well said, then, that by performing just actions one becomes a just person and by performing temperate actions one becomes a temperate person, and no one is going to become good by not performing these actions. But most people do not perform them, but believe that by taking refuge in talk they are philosophizing and in that way will be people of serious stature, doing something similar to those sick people who listen to the doctors carefully but do none of the things they order. So just as they will be in no good condition in body if they treat themselves in this way, neither will those who philosophize in this way be in any good condition in soul. (1105b9-18)
I think I will memorize this quote and repeat it daily during Lent. It certainly, for me, summarizes the essence of repentance: put up or shut up.