Our minds are unreliable devices. Our memories are not perfect copies of reality but are constantly being rewritten and reimagined to suit our own needs, until the people from our past are no longer an accurate representation of themselves but instead are seen through a filter of our own hopes or issues, often to an exaggerated extent. One of the best ways to resolve this is to meet them again. Allow your brain to recalibrate to reality and remind yourself why they are no longer part of your life. Then your mind can put the issue aside. Closure.