I hate that shit fr. Leave me alone I am literally just trying to vibe
Remembering that people's lives progress and change when you're not around them and you really only know who a person was the last time you happened to see them and you talk to someone you haven't seen in a while and they're not quite the same person as before, they merely resemble the person you remember in your head and you're not the same person they have a conception of in their head because there is no permanent self and no objective viewpoint by which one person can be seen as the same person by multiple observers.
I live this. It's why I've become a literal shut-in with almost no social interaction for months at time despite being soul-crushingly lonely. Even before Covid, I could barely leave my home (and I know I'm lucky as fuck to even have one and be able to stay in it). So yay, big mood.
They're both horrendous. Solipsism can become a kind of coping strategy when this^ gets particularly bad.