When someones poor choice effects you, it's hard not to react in an outburst, or hold it against them. People carry hate for people their entire lives. Maybe you are in the right, but how does keeping that chip on your shoulder help you?
A time comes where you have to move on, not to take that anger with you anymore. It's not good to bottle emotions, its healthy to release them.
Sometimes You get so boiled up that you forget that you must forgive to move forward. Carrying that emotional burden on your shoulders is heavy, takes up space and can even manifest itself physically. Forgive and set all your baggage down.
"Bitterness is a poison you swallow, hoping your enemy will die."
Let it out, then let it go. What is your healthy outlet? Exercise? Music? There are many outlets that help you get rid of the negative emotions that are hurting you. You cant change the past but you can change the way you see the past. Where there is pain there is power. What have you learned from it? You have to let it go if you want to move forward.
Other resources:
The Difference between Happy and Unhappy People
When to let go and when to Fight On!
What you Plant in your Mind, Comes out in your Life