If you do good, you must do it only for God. For this reason you must pay no attention to the ingratitude of people. Expect a reward not here, but from the Lord in heaven. If you expect it here — it will be in vain and you will endure deprivation.
+ St. Ambrose of Optina, quoted from Living Without Hypocrisy: Spiritual Counsels of the Holy Elders of Optina