Is there anything that we can do besides just praying?
Grieve.
i don't have the exact verse handy right now; but, it is something to the effect of capturing ones mind and bring it under captive of Jesus Christ.
It's quite hard to do mind you.
I have dealt with bitterness.
A lot of gruesome past has happened to me since I was a little boy that will take too long to be explained here (but, basically, it involved traumatic abuse: physically and mentally. and when I say abuse.. I am not talking about spanking.. but a real abuse where it involves going to hospital. But, since I was born in 3rd world country, things like that get overlooked by the law. So, I have to endure the experience until I grow up strong enough to actually fight back. I was a messy kid back then. Lucky, Jesus Christ catch me be4 it was too late).
but, speaking from experience:
1. You need God (obviously). Without Him, there is no way for you to be able to let go.
2. You need constant obedience and prayer.
3. Slowly changing the hatred into love by healthy and constant relationship with God.
4. you need to take the focus out of yourself and into others. Volunteering, helping people, and doing selfless deeds help putting a godly perspective into your life. Suddenly, you realize that your life isn't so bad and you stop becoming the victim.
You become thankful to God and realize that harboring grudge done nothing for yourself and others.
In my case, God helped me see a perfect image of a father.
Thus, I am able to forgive my dad for countless horrible things that he did to me.
Now, I am at peace and I am in good term with my dad.
Last night, I had a dream hugging my dad and thanking him for things he did (good and bad).
I suddenly realized that he was not perfect and no matter what he is still my dad.
Hope that helps a bit.