Bitterness gets into everyone's life at some point. I've known people whose lives have been shaped and ruined by bitterness. Dustin Neeley has written a helpful post about how to deal with bitterness. His outline is just as valid for any person and doesn't just apply to those of us who find ourselves in the position of pastoral leadership.
He offers the following suggestions:
1. Take it all to Jesus.
2. Forgive the offending party even when they don't ask to be forgiven.
3. Turn off the movie in your mind.
4. Filter the experience through the lens of Scripture.
5. Pray for the person who hurt you.
It's not rocket science, just plain and simple discipleship stuff. You will need to read the whole thing to get the fuller picture. Here's the link.