From Lovers To Just Friends

Is it really possible for a man and woman that used to be lovers just become friends? Once that line of intimacy is crossed and there are mutual feelings, even if the feelings aren't exactly the same can it work? There are times where two people start as friends, have sex and continue to be friends. That to me seems to be an easier situation. There probably wasn't that relationship type love. It was just sex. But for those people that crossed the line with sex and more can they go to being friends as if nothing ever happened? This is a topic I am really curious on getting opinions on. I my self have never been friends with someone that I had a relationship with that went beyond sex. I usually cut people completely off never to talk to them again. Or most of the time the relationship ended in anger so there was no need to talk or speak to that person ever again. But if the relationship didn't really end but both parties just decided to be friends, will it work. What if they were in love with each other but could not get the relationship to run smoothly, will it work. So basically I want to get peoples views on this topic. I don't think it will. I think someone will end up jealous if they see the other one with another person. Especially if they really love the person and didn't want it to be over. There might be some resentment. So people do just read, respond. I would love your input...