1. incapable of being held by one person at a time
2. incapable of association or harmonious coexistence
3. incapable of blending into a stable homogenous mixture
In the movie, "the Holiday", Iris would never have known how wonderful Miles was if the "other guy" hadn't been so wrong for her. Sure she loved the feelings she got from him and the sex was amazing however, they were incommattible.
As the "other guy" goes, he played an instrumental role in the girl finding the right guy for her...Matt has a significant part in your life; don't hate him for that.