Let him never cease from prayer, who has once begun to pray, even though his life is ever so bad. For prayer is the only way to amend one's life and without prayer it will never be mended. Let him not be tempted of the devil, as I was, to give up prayer on account of one's unworthiness. Let such a one rather believe that if he will only repent and pray, our Lord will still hear and answer.
Teresa of AvilaWhile the soul is in mortal sin, nothing can profit it; none of its good works merit an eternal reward, since they do not proceed from God as their first principle, and by Him alone is our virtue real virtue.
Teresa of AvilaAnyone who has the habit of speaking before God's majesty as if he were speaking to a slave, careless about how he is speaking, and saying whatever comes into his head and whatever he's learned from saying prayers at other times, in my opinion is not praying. Please, God, may no Christian pray in this way.
Teresa of Avila