One of the first things Jesus does as He is driven by the Holy Spirit is prove that He has the authority to forgive sins. He proves this by proclaiming forgiveness and then, when challenged He winds up healing a paralytic man. As with many things that Jesus does, we focus on the physical miracle, and not the spiritual one. Jesus teaches forgiveness in the Lord's prayer. He authorizes forgiveness when He rises from the grave. When we forgive, we are not only doing what Jesus wants us to do, we are being, practically, as much like Him as we can be.
The effects of forgiveness on the world around us are always powerful. Grudges are torture for many people who need to be set free and the enemy hates it when we are not in chains. So, it makes sense that forgiveness would be too hard for us on our own, but Jesus promises that when we ask, when we agree together, when we come to Him in His name, He gives us everything we need to forgive even when it is too much for us on our own. When we do this, people will see Jesus Christ in us. They may or may not come to believe in Him because darkness does like to hide from the light. However, as the Centurion realized when he witnessed Jesus proclaim, "Father, forgive them, for they know not what they do," he was seeing the Son