I absolutely understand you ™. What you are describing is the struggle between our instinct and the learned cultural experiences. When you imagine being with someone, you’re just crossing the limits of culturally modelled relationships.

For our old brains, evaluating another companion is transparent, it is just good old evolution again.

I don’t want to feel guiltiness when I imagine how would be this and that… It is perfectly normal to think, when you can’t act. We should value what we really want, hefting the emotional part and the rational and*

*(as if it was easy to decide if feelings are certain or just passing thoughts, as if one were better than the others!)
What a cruel decision, the tragedy of choosing!