In today's Gospel reading from Matthew 6, Jesus taught his disciples how to pray by saying the Our Father, the most appropriate and beautiful prayer there is. He emphasized the importance of the forgiving-others part by further adding: "If you forgive others their transgressions, your heavenly Father will forgive you. But if you do not forgive others, neither will your Father forgive your transgressions."
We must absolutely take this last saying gravely. Forgiving others is often most difficult for us to do. We could decided not to forgive the person, which amounts to shutting the door in God's face – outright disobedience. Or we could admit to God that it is difficult for us, and so we need his help – this is keeping the door open. These two opposing stands display the fundamental difference! Should you choose not to have the Father forgive your transgressions, you have to be the biggest fool in the whole universe!