Someone said somewhere that people in unhappy marriages should leave the relationship and then start looking for someone new, surely those marriages that end due to one partner leaving for a new relationship, that do actually end in love (my Dad and his OW for example) the point is they have already met this person, and fallen in love, we can't choose when we meet someone so I don't think that can really be followed.
Wait until we end a relationship before moving on , yes, definitely, we don't have to act on our feelings, but how we are suppsoed to not have those feelings in the first place is beyond me.
When I was in an abusive relationship a friend's brother was my shoulder to cry on, he was lovely, under different circumstances we'd have been a couple, we had discussed it on numerous occasions, he'd let me know that if I ever wanted to I could end my relationship and be with him, he knew I felt the same but was in a relationship.
We never crossed that line, even when the only pErson we would have been betraying was a violent, drug-addicted, alcoholic who was sleeping with anything that moved. Which is why I believe our feelings aren't possible to stop, but our actions are.