My perspective is that if you just lose someone completely through divorce or whatever, you hurt a lot for a long time but it slowly gets better. If you are in a situation where you have the option of allowing that person to continue loving you despite also loving someone else, can you appreciate the attention for what it is or will you only ever be able to focus on not being the only one? What I have noticed in my divorced life is that I end up becoming friends with women who have active love lives and tell me about them. I don't end up dating people but I enjoy the interaction and attention more than when I'm completely alone.
So what I would really recommend to you would be to live completely alone for a while until you are getting over the pain of separation and loneliness and then see if you would rather have a shared relationship than no relationship. Of course, it might be hard to actually take that alone time without losing your partner completely but, at least in theory, it would allow you to heal from the pain and see what you want out of a relationship in a pain-overcome state. Probably others in this forum will have advice for you about how the pain-healing process goes when maintaining a relationship with a partner you share with another person, though, too.