If you feel you can’t forgive, ask God to penetrate your unforgiveness with His love. When we have to do the impossible, God says that the way it happens is “not by might nor by power, but by My Spirit” (Zechariah 4:6). This means that certain things will not be accomplished by human strength, but only by the power of God. The Holy Spirit will enable us to forgive even the unforgivable.
