I suspect you need to define forgiveness for yourself. In my mind it is detaching from resentment, anger and other negative emotions about the person -- a letting go of the incident.

My dictionary defines trust as a "firm reliance on the integrity, ability or character of a person or thing." It seems to me that that is a very different thing from forgiveness. If you know that someone has a drug or alcohol addiction which is out of control and they are very hurtful to you, you can forgive them because it is truly the "drug" talking. But, until they get help, there is no use trusting them because lying and manipulation are a large part of the disease.

Does that help?