how do u move on from the fact that not everyone around u is staying forever

i feel like i am the only person who thinks about this everyday, every hug every moment i just think how i'm gonna be thinking about these moments while grieving later and suffering, and it hurts so bad thinking like this everyday, my therapist told me that we humans are wired to get over it and move on when people around us die but i just can't stop thinking about it, do you really just suffer and get over it?