Forgiveness is giving up ill feelings (anger, resentment, bitterness, hostility, etc) and our right to retribution no matter what they have done to us or someone we love. Even if it happened to someone else, we do not have a right to seek retribution in any form because revenge is under God's control in our lives. (Romans 12:19) We must also forgive ourselves for our failures. Unforgiveness is rebellion against the Almighty, and that makes it serious business with serious consequences. We need to take care of it immediately.
I believe this verse is telling us that if we face the reality of the condition of our own souls, the things our "brother" does to us will seem much less significant. This has been true in my life. When I examine closely the things I have done over my lifetime, the motives in my own heart, and am real about how weak and unworthy I am without Jesus, the stuff done to me and mine shrinks. We need to get busy dealing with our own sin rather than being angry at what someone did to us.
If we are actively seeking to limit our sin and grow closer to the Lord, we will not have much time to look at someone else's sin. I love how God uses wood in this comparison. Growing up around construction, I know there is very little you can make with sawdust, but if you take a plank out, you can really build something solid with it. The more planks you pull out; the more you can build. The more sin we pull out to deal with, the more we can grow.
To deal with the sin of unforgiveness, we need to realize it is serious and has serious consequences. We need to acknowledge that our unforgiveness is the opposite of love and has caused harm. We need to confess our guilt to God and ask His forgiveness. We need to ask God to help us truly forgive. Then we need to take action.
When those angry and resentful thoughts come into our minds, we choose to let them go and think with compassion, grace, and mercy. When I have those hard feelings come up, I ask God to help me with the process of forgiving and to bless the other person. Sometimes I have to pray that for many months before forgiveness comes. Other times, forgiveness comes quickly.
If God leads you to go to them, don't list their sins against you. That will fuel their anger, and make them defensive. If you've forgiven them, then those things don't matter anyway. List yours against them and apologize. Talk about what you wished you had done differently. Don't worry about their reaction or what they say. If they won't meet your attempts at communication, don't worry about it. This is you obeying Your God, and you will reap the blessings for it.
It's a sad situation when people really do care about each other, but would rather hold onto hurt and resentment rather than extend real love through forgiveness and understanding. Holding on to it is selfish while letting go of it is selfless. Being fearful of more hurt is selfish. Our trust should be in God with the confidence that doing it His way will bring us great reward on earth and in Heaven. If they claim to be a Christian, and you claim to be a Christian, then glorifying the Lord with your reconciliation should be the main goal. It doesn't mean you have to see them every day. It means you have taken steps to live peacefully, can come together in peace with godly love.
Instead, what we do see so often in our Christian families and churches is people rebelliously holding onto resentment and anger and even passing it on to other generations or people outside of the situation. This is not fitting for the Body of Christ! Satan is known as the accuser. When we choose to hold onto accusing and not forgiving others, we are like him. Unforgiveness is actually satan's most effective weapon in our churches and families today. The Bible even warns us that unforgiveness gives satan an advantage over us!
I Corinthians 2:10-11 Anyone you forgive, I also forgive. And what I have forgiven—if there was anything to forgive—I have forgiven in the sight of Christ for your sake, in order that Satan might not outwit us. For we are not unaware of his schemes.
We should be like Paul and saying to our friends "I have been obedient and have forgiven my offender. I am asking that you forgive them too. This way, Satan can't outwit us and interrupt God's work through us."
I Peter 3:9 Do not repay evil with evil or insult with insult, but with blessing, because to this you were called so that you may inherit a blessing.