Huge sadness drop after hanging out with FP?

My FP only had 2 hours to hang out today but he originally only had time for 1 hour but he made room for a little more time for me, hanging out with him is the actual highlight of my day but after we finish hanging out I always have such a huge drop in mood... almost like the mood you get in after sex/having a bdsm scene and that feeling you get for aftercare. It sounds dumb but it feels like I need aftercare for a goodbye... does anyone else understand? All my previous relationships have been so intense hanging out 24/7, sleeping on call, never being without each other so I guess I never experienced this drop as much? I always end up doing stupid things like contacting my ex or just starting fights with people who aren’t him because I feel like I’m suffering. It’s dumb.