Maybe it’s just me, but I find myself talking myself up when I’m alone. I literally think I’m the funniest person that I know and when I look in the mirror I don’t dislike what I look like. But when I’m around other people I’m often surprised when they actually want to be around me or be friends. Most of the time I can’t even imagine the guys I hang around could even see me as anything but gross. 
I just realized this thought process the other day and I’m wondering if it’s my own insecurities talking or if it’s a BPD thing?