Many see Jesus' Sermon on the Mount as a blueprint for human behavior. But to do so is to turn it into another form of legalism.
Jesus did not give us these words so that we could grit our teeth and fall into despair because we cannot follow His path to perfection. He gave it so that we could recognize the distance between ourselves and God. To become aware of the great chasm that is in that distance. It is given so that we may know that all humans stand on the same level ground before God. No sinner is worse than another.
When we come to know that all have fallen short of the glory of God, we can rest peacefully knowing that God cradles us in His arms and covers us with His absolute Grace.