You're a different person now, it's just sad because I miss you a lot. Strangers can become best friends just as easy as best friends can become strangers. Friends and family members evolve over time, we all do, so this is a sad but true fact of life.
This describes my feelings perfectly: "I actually really love when someone remembers small details and quirks about me or addresses me by my name at unexpected times like at the end of a sentence and I don't know why but I just really, really do.
The person might not be who you thought they were; might have changed for the worse; but in the memories, they will always be the person you loved. it's ok to cherish those memories. You dont have to allow that person in your life now.