How do I forgive others? First, know that God is on your side. He reveals this again and again in Scripture and in our own stories, that whatever we surrender to him, he redeems.
Forgiveness is a difficult and complicated subject. When we are betrayed it affects us on many levels, some of which (perhaps much of which) we are not aware at a conscious level. The key is releasing persons from responsibility and then turning to Christ, who has taken all sin to the cross, including the sin against us by others. So it is a constant turning to Christ, receiving his love and releasing his love for others in the form of forgiveness and also in other positive ways of showing love.
There can be layers of pain on the inside and as those layers get exposed by various triggers, I simply remind myself and God, I've already released that so I will allow God to have it and ask for his healing of my pain.
The seminal story of forgiveness is Joseph. In Genesis 50, after Joseph's father dies, his brothers fear he will use his power (which was considerable) to punish them for their betrayal of him when he was a young man. He says to them: “Don’t be afraid. Am I in the place of God? You intended to harm me, but God intended it for good to accomplish what is now being done, the saving of many lives." Genesis 50:19-20 (NIV)
It's an amazing story of forgiveness. In essence, he says that God is the one whose rightful place it is to judge and punish and that God had actually turned a terrible betrayal into a tremendous blessing. God is in the redemption business.
So, by faith we turn to God and continually turn over our hurts and our hearts to him, seeking our own forgiveness and healing for the hurt others have caused us. I can't imagine how many times over the years Joseph had to turn to God in order to deal with the hurt and pain his brothers inflicted on him. We are just seeing the end result of many, many years of faithfully turning to God every time he felt the sting of that betrayal.
So, forgiveness isn't easy. It's not flippant. It has far-reaching consequences, and when we over and over turn to God, he is always faithful, always merciful, and always forgiving of us for our sometimes sinful responses to the hurts in our lives.