This means that you could go to God throughout each day confessing your own sins, but they remain unforgiven if you are harbouring unforgiveness towards others- even if it was a lifetime ago or a recent event. There is now way around this. It is non-negotiable in God's sight.
God, we realise now how crucial forgiveness is. Even if we cannot go and say sorry to the person WE have sinned against or THEY have not said sorry to us, then all that matters is bringing it to You. I have forgiven many people major things in my life without contact with them - this was done through You and I gained the blessing of Your presence through that and gained forgiveness which left nothing between us. Thank YOU, Lord that it was YOU who helped me forgive some of the people. Because I asked You to help me with this. Thank You too that You do this to anyone who asks the same. Amen.