1 Yesterday I said “Blessed be God!” and today again I say the very same thing. For although the evils we dreaded have passed away, we should not suffer the memory of them to disappear; not indeed that we may grieve, but that we may give thanks. For if the memory of these terrors abide with us, we shall never be overtaken by the actual experience of such terrors. For what need have we of the experience, while our memory acts the part of a monitor? Seeing then that God has not permitted us to be overwhelmed in the flood of those troubles when upon us, let us not permit ourselves to become careless when these are passed away.
Then, when we were sad, He consoled us, let us give thanks to Him now that we are joyful. In our agony He comforted us, and did not forsake us; therefore let us not betray ourselves in prosperity by declining into sloth. “Forget not,” says one, “the time of famine in the day of plenty.” Therefore let us be mindful of the time of temptation in the day of relief; and with respect to our sins let us also act in the same manner. If you have sinned, and God has pardoned your sin, receive your pardon, and give thanks; but be not forgetful of the sin; not that you should fret yourself with the thought of it, but that you may school your soul, not to grow wanton, and relapse again into the same snares.
Source: Homilies on the Statues (New Advent)