A big part of being human, is having friends, and other various relationships. Today, someone may re-enter your life suddenly, and unexpectedly. This is the opportunity to make ammends and start a new relationship with that person.
What if that person is on the "wrong spectrum of life"? Who are you to judge? If they come to you with an addiction, maybe they need your help getting out. If they come to you with drama, maybe they need your good insight to a terrible situation. Your small interaction, could be the catalyst that saves a life.
What if it's a romantic tie? You mean an ex gf? Ex bf? Leave it at exes and become friends. If something happens in the future... so be it. Life is only what you make of it, and right now, you are the one in control.