PTSD is an understandable reaction to extreme circumstances. It doesn't mean that you are weak. It does make it more difficult to handle further stress, and when you have been through trauma, of course that harms or damages most people. The trauma isn't your fault. Neither are the symptoms or effects of the trauma your fault, but therapists will try to help you to understand how it impacts you and the people around you, and process it so that you can live your life more effectively, have better relationships and more success, etc. Forgiveness doesn't mean that what the abuser did was ok, but letting go of it is important for our healing because it will keep us stuck if we refuse to let go of it.