yo! INFP here as well.
I had a strange experience at a friend's get-together a couple weeks back -
After our musical performances (it was a get-together for musicians - we all played classical pieces we were working on) I was mingling as one does at such functions. I remember genuinely enjoying the conversations, then suddenly, halfway through somebody's sentence...
...it stopped being fun. I was done. I was tired. I needed to be by myself. I was surprised how suddenly this came about - as if someone flipped a switch inside me. I came with some people, so I didn't want to rush them, but it was such a chore engaging in the chit-chat until it was time to leave.