You talk a lot about how forgiveness lowers one’s anger. You further state that too much anger is unhealthy for a person. Yet, isn’t it possible for anger to linger for a very long time when someone close to you betrays you?
Yes, you do make a good point. When betrayed by a loved one (and many other examples of injustice), anger can continue for a very long time, even years. Yet, there is an important difference between feeling some anger as you recall what happened and being dominated by intense, unhealthy anger. Forgiveness, practiced patiently over time, can reduce this unhealthy form of anger. Having some anger left over simply shows that you are human and you are still, legitimately, responding to what happened to you. You are saying that you are a person of worth who should not have been treated this way. So, I think you can go in peace knowing that you have forgiven even with some residual anger. If you are feeling the intense, toxic anger on a regular basis, I suggest that you turn once again to the process of forgiveness to lower that anger.
For additional information, see How do I know if my anger is healthy or unhealthy?