Take heed to yourselves: If thy brother trespass against thee, rebuke him; and if he repent, forgive him. And if he trespass against thee seven times in a day, and seven times in a day turn again to thee, saying, I repent; thou shalt forgive him.
Why are we supposed to forgive like this? If a brother came to me even three or four times in a day asking for forgiveness for the same thing, I would begin to doubt his sincerity. I would find it increasingly more difficult to forgive him. How can God ask us to do this? I believe He does so because it is how He forgives. Yes, I know, "...for man looketh on the outward appearance, but the Lord looketh on the heart." (1 Sam. 16:7b) I believe He is looking for any excuse He can find to forgive us. He wants to forgive us. He died to forgive us.
This does not mean we have a license to sin. His forgiveness takes care of any and all eternal punishment that sin may cause, but there is still temporal punishment for sin. "Be not deceived; God is not mocked: for whatsoever a man soweth, that shall he also reap." (Gal. 6:7) Sin always has some consequences. But God be praised, He will always restore our fellowship with Him through forgiveness.