Old friends

Hi, guys. Today I went to a birthday party of an old friend of mine which I haven't seen for a while. About 2 years ago I used to study at a German school here in my hometown but a semester in the school year I transferred to another high school because I really wanted to study English.
I had to say goodbye to my old classmates and move to a totally different school with other subjects. I managed to stay in touch with my besties from the old school for a while but when I befriended my new classmates and we just lost connection but I missed them all, so you can imagine how happy I was when two weeks ago I got an invitation for the birthday party of one of the girls I was closest to back then.
Fast forward to the party and as I enter the apartment all of my old friends are staring at me with confusion. It took them quite some time to recognize me, I believe, but when they actually did I was welcomed with a lot of hugs. We danced, laughed and ate but I was actually really surprised by the people I used to know. (da song reference, YO!)
Anyway, everything was fine, it was really fun but I'm just kind of disappointed that they have all changed so much and became such amazing people and I haven't been there for them! One of the girls I was really close is now dating another girl. Another old friend of mine is now working as a model! All this is great and I'm really happy for them but I just wish I had spent more time with them!