Does forgiving require me to abandon my psychological defense mechanisms altogether? What if in the future I need a little denial to protect myself from intensive anger or anxiety?
To forgive in one context, let us call it Situation A, does require that you reduce the defense mechanisms that prevent you from seeing the depth of your own hurt and anger. This can be done slowly and gently.
Your having lowered those defense mechanisms in Situation A does not mean that you will have lost your natural ability to have defense mechanisms in the future. In other words, breaking denial in Situation A does not mean that denial will not operate well in Situation B. Denial still will need to be slowly lowered in Situation B if that denial is not allowing you to see that you are angry, that the anger is compromising your well-being, and that you need to do something about that anger.
Read more about dealing with defense mechanisms in Forgiveness Is a Choice.