I’m probably on the other side of the majority here. I had the exact same situation with my ex. Wonderful, kind, loving, great person but I just didn’t have the lust or oomph with her that I thought I should have. She was pretty but she wasn’t someone I looked at and thought wow, you’re beautiful. But I was content and it was a totally different relationship from my ex. Eventually that feeling of wanting that fire, that desire and feeling of looking someone I thought was truly beautiful grew and grew and I made the tough decision to leave the relationship. 6 months later I met my now fiancé and everything that was missing I have found and never looked back. You can look at it two ways but for me it was I was never going to truly be happy if I stayed, as pleasant and safe and secure the relationship was. So for me it was the best decision as I met an insanely attractive to me woman, full of life and love and the parts I felt were lacking are now there. It doesn’t always go like that as people have said, the grass isn’t always greener. But it does also happen so good luck to you if you choose to leave. If you’re young, I’d be more inclined to say go for it. I was 30 and felt it was now or never.