I found understanding this distinction really, really helpful. I was struggling with feeling that maybe I was not compatible long term with my partner and though we’d talked about it many times and I felt sure that he loved me deeply, it was like I was missing the language to talk about commitment and what I needed. Most of the second part of the book (reading the third part now) was so comforting, reassuring and helpful in giving me perspective. If you’re having a similar struggle I recommend reading it. It’s more focused on a couple transitioning to non mono than being poly and dating, imo but despite that a lot still resonated.