They are very important. unforgiveness is a sin and the Bible says that we cannot continue in sin and say that the grace of God should abound.  When we forgive we will also be forgiven by God of all our sins.  It is then that God will answer our prayers.  Also when we believe that whatever we ask of God He will answer us, it then that we can even Ask from Him.  So believing and forgiveness is a key to effective prayer.