Having memories with those you were close to is a good thing as part of re-creating that feeling of warmth, connection and joy. Everything is temporary and the Buddhist Noble Truth is that clinging causes suffering. If you are not holding onto the past then as I said, it’s a good thing to have such fond memories.
I think there’s a lot to be gained by reflecting on your past memories with people. Sometimes you’ll learn new lessons, and other times you’ll simply be reminded why they’re no longer a part of your present.
Do you feel like reminiscing on people from your past is negatively affecting you?
P.S I lost touch with my best friend, we were friends since the age of four. We reconnected after fifteen years, our friendship is stronger than ever, of course it’s not the same but if anything our friendship is more authentic than it ever was so it’s not always the case that you would drift apart again.