Whether or not you try to become more compassionate, one thing still is likely to happen: You will change. Life is about developing and therefore we do not stay static. You have been hurt and your trust has been damaged. As you practice forgiving, you are correct, you likely will change. You likely will become more compassionate and more trusting in general (but not necessarily toward those whom you should not trust). If you notice, those characteristics of compassion and trust are positive developments. Forgiveness could help change you in very good ways. Try to enjoy the positive transformation.