The first step to letting go of anger is to identify it. Know what it is that is truly making you angry about a situation. Anger can be a blinding emotion. When you are angry about something, often that anger can be directed at anyone in your path. This is really not constructive anger, and it can hinder relationships with many people.
For example, when my first husband left me.....I was angry. I lashed out at him, my children, his family, my family, myself. Then after he got remarried, a lot of my anger was directed at his new wife, for reasons I will not go into here. Needless to really say, that marriage has since dissolved as well. I was destructive and damaging. It was not a good situation at all. I carried that anger with me for a really really long time. A while ago I decided to really reflect on that anger. I asked God to please help me let go of it, as it seemed to consume me. I realized that a lot of my anger was at myself. I finally admitted to myself that I was not blameless in the breakdown of the marriage. I made some fatal mistakes. Of course, so did he, and it was the accumulation of mistakes that lead to the final break up.
It was in the realization of what I was really angry about, that finally set me free of that anger. When I owned the anger, embraced it and admitted it, I could finally set it free. And by setting it free, it in turn set me free.
It is the key to freedom from debilitating anger and resentment, to identify it and own it.