The reason that Paul gives for letting go of our anger quickly and being forgiving is not the commandment "Thou shalt not kill" (as Jesus cited) but that we are all members of the same body. The longer we wait, the harder it is to be rid of the anger, and the more damage we do to the body. Damage to one part of the body affects the entire body, including us, and the head of the body which is Christ Jesus. Letting our anger linger and not dealing with it quickly is sin against both God and man.
For reflection: What anger and resentment is still lingering from my childhood?
Let us pray. Jesus, I am guilty of letting my anger linger and fester, sometimes for years. Help me to get rid of all the old anger, resentment and unforgiveness in my life. Please bring to mind all those I need to forgive and set free.
(After praying a prayer like this, pay attention to odd thoughts you have, people or incidents you haven't thought of in years, or dreams that you have about the past. God's speaks to us through these thoughts and dreams.)