Jesus says over and over again, "But I tell you..."  This is so important.  This means that the old testament laws are fulfilled and now Jesus strengthens those laws with His mercy, grace, and love.  How many times in the Sermon on the Mount has Jesus said, "But I tell you..." ?

Jesus is telling us here not to seek revenge.  It just isn't important.  Jesus wants us to go the extra mile, turn the other cheek and give to those that ask.  Do not try to get even.  Jesus tells us that we have a higher purpose for our lives. Jesus is asking us to walk on a higher ground.  That higher ground is compassion.  He wants us to show others compassion so that we can show the love of God through our actions.  That makes Jesus very happy