Reliving the past

Lately, I've just been reliving happy memories and realizing I'm never going to experience those things again. Like memories of hanging out with my friends and knowing that even in that moment I was thinking about how I would be sad looking back at it. I know that's a pessimistic way of looking at it, but it really is just sad for me. Next year, I'm returning to this club at uni, but it makes me sad because everyone will be different and all of the people I cared about will not longer be there. I don't want to make new memories in this club without them, especially because I've spent years with them doing the same thing. It's a shock to my system and I'm at a loss on how to move forward.