We need to make a distinction between being forgiven of something and being done with something. This is a matter of justification, regeneration, and repentance. Transformation is a process. Just because someone has been forgiven of their sins by God, or forgiven of a particular sin, by others, this doesn’t mean that the person doesn’t still have a sinful problem.
The power of sin is not instantly fixed through forgiveness. By virtue of justification, the eternal penalty for sin, and being guilty in the eyes of God, that is “fixed”. But there remain consequences in this life. Sinful patterns must still be dealt with. By virtue of regeneration, Christians do have the power to overcome sinful patterns, but they must endeavor to do it. It is not automatic. It takes time, effort, and commitment. Christians should forgive, but they should not act as if their forgiveness of a person, or even God’s forgiveness of a person, means that person is fully and finally healed of their sinful pattern.
There is a difference between repentance proclaimed and repentance proven. Repentance proclaimed (a confession) begins in a moment of time. Repentance proven (a conversion) happens over the course of time. When repentance is proclaimed, we forgive. When repentance has been proven, then we forget. To do otherwise is not wise. Trust takes time.