Unforgiveness is not seen physically, many Christians feel that they can get away with it. But it is deadly if it is left unchecked in your heart. God will not hear your prayer, and He will not prosper or bless you if unforgiveness lingers in your life.
God will be angry with you, because He forgave you, but you would not forgive others! Remember, the bible tells us the Lord was wroth with His servant for not forgiving. In addition, the bible says the man who did not forgivee his brother was handed over to the tormentors.