Take control of your thoughts, when those impulses surge, purge them away. In time they'll lose their strength over you.
These days was watching some talks by a monk and while talking about that psalm that talks about vengeance and smashing the enemies children against walls. He said those children were thoughts as they first appear, without much power over us, so we defeat them in that stage while they are weak. If we let them fester and grow up they'll take control of our minds and lives. Be it through anger, depression, whatever.
So do as Paul says: "take captive every thought to make it obedient to Christ."
In the meantime while you are not used to this and fall prey to those grudges, plead mercy to God when it happens (example: Lord Jesus Christ, Son of God, have mercy on me, a sinner) and ask for His help in overcoming it.
God always answers our prayers that have to do with our sanctification and salvation of our souls.