I don't know the details of your problem, but I will try to help.
There is no easy answer, but honestly I don't think we can forgive, at least not on our own. That's why the Lord says in the Bible, "Let my grace by sufficient, for my power is made perfect in weakness.
What this means is that when we are weak to do something we must rely on the grace of Jesus Christ to help us through.
You ask, how can you forgive someone who almost destroyed your family and your life?
Now ask how can Jesus forgive the very people that scourged him, spat on him and nailed him to a cross. How can Jesus forgive a world that is constantly rejecting Him, criticizing Him and would much rather see him dead and never hear from him or about him again.
Don't forget that Jesus also suffered, the Lord God became man and suffered for us. He is God. He didn't have to suffer, He could've used all his powers to escape his suffering, but He didn't, but chose to suffer instead.
For what purpose? So that in his suffering he can relate to us and we can relate to him. He can say with all sincerity and honesty, I know how you feel, I felt your suffering at the cross. I'm also suffering with you and I will help you get through this.
Jesus forgave you for all your sins, past, present and future. He forgave you when you didn't deserve to be forgiven. So forgiving is not a question of do they deserve it or not. You forgive because you were forgiven.
But that's not the only reason to forgive. It's also for your own good. When you forgive you're not only setting the other person free but your also freeing yourself from the bitterness and hatred that can eat you from the inside out and can affect your health and your relationship with other people.
Again, I don't know the details of the problem. If this is a person who is causing you physical harm then forgiveness is not tolerating what he does. If this is a person who is constantly cheating on you, then forgiveness is not accepting his behavior.
Forgiveness is saying, in your heart, I'm not going to judge you. I'm not going to take revenge for what you did. Judgement and revenge belong to God. I'm setting you and myself free.
I hope you can get through this situation, seek the Lord's help. He can help you forgive. I hope his grace and his peace will dwell n your heart.
Wish you the best.