Think about compatibility and the difference between Mr. Right vs. Mr. Right Now. Someone doesn't have to be a bad person to be wrong for you.
Exactly. My character feels this when she makes her choice. "I love No. 2 too, but not enough. In a different way. I have a feeling that after a few years, the charm of his stories will fade, and he will become just another person like any other. What would I do then? I am attracted to him, but he isn't meant to be my everything. Just a friend, more special than all. With No. 1, we have been best friends before being lovers, and we are thinking in the same way. We would never get bored together."