If you had know what this means, "I desire mercy and not sacrifice, you would not have condemned the guiltless. (Matthew 12:7)
A self-sacrificing lifestyle is a life measured by what is done or not done. It says, "Look what I have not been able to do; am I not a good person!" Therefore this lifestyle will be filled with judgements because others have not sacrificed in like manner. Jesus is telling the Pharisees that a right relationship to God is not based on do's and don'ts but on mercy. We are rightly related to God not by a list of rules and regulations, but by His mercy and His mercy alone. Therefore Jesus is saying, that since we have received this mercy we in turn are to be merciful. Whenever we judge another believer by our own standards, we most likely are the guilty judging the guiltless. It is not a matter of "I do this and that," but it is a matter of what God has done and what He is doing. Remember Jesus Himself has said, "I desire mercy and not sacrifice." Therefore, let us be merciful.