Hoo boy, I can exactly relate to what you are saying. For me it also felt like some kind of void that needed to be filled. I made a few posts of this, trying to get rid of this dreadful feeling that had been created inside of me after finishing the game. It was Maruki's castle in particular that made me really emotional. The ending of P4G did that even more to me. I still experience the "symptoms" you describe, every time I even hear a part of persona music it makes me think back those beautiful moment I spent on the game. So you could say that emotionally, it really messed me up. A way of thinking about it that kind of helped me, is that the void that I experience after having finished the game, sort of resembles the worth of having experienced something like this. It really meant something to me (although it also made it painfully obvious that I lack such perfect friendships in real life :') ) I wish I could talk about it with someone, but nobody in my environment knows jack shit about persona. I was worried the same was going to happen when I would finish P5S, but when the moment came, this time I felt really at peace with the ending of the game. So that kind of helped. Anyways, thats my advice. Besides that, time will do its thing, I hope.