I've only been living my poly tangle for a few months, but I love to share what I learned about this in my mono life.
A very wise woman recommended to me to take 40 days and 40 nights in between that change of a relationship. She recommends it also for going from friends-to-lovers, but I have only done it after a break up. All the people I have successfully done this with, I am still friends with. All the people with whom I did not do this, I am not friends with.
(I did so much I got good at it, which I'm not necessarily proud of. serial monogamy has it's pain)
So, when there's a decision to break-up, be it mutual or not, you have a conversation. 'I like to take a break, to give me time to heal. I request we have no contact for 40 days and 40 nights. *pull out a calendar* We can meet on thus-and-such a date.' Pick a place to meet, I recommend neutral ground. The meeting is to re-connect, talk about whether we'd still like to be friends, or whatever. During the breakup conversation, you work out any details. I knew a couple who did this, but there was a kid birthday in the middle of the 40 days, so they negotiated how to do that. I was owed some money, and I said, 'give it to friend X, they can give it to me' I did have one that ended a few days early, my truck had broken down, and he was a mechanic, and graciously saved me. Although, I stuck to my agreement, and asked another friend to call him for me.
For me, it prevents me from saying or doing stupid stuff in the heat of a regretful moment, or a grieving moment. I tend to write a lot, but the no-contact makes me not send them. It prevents drunk dialing. It gives me time to remember who I am as a single person (because i had a tendency to forget that in overzealous pair bonding). :P There's also a commitment on my part, to not enter into new relationship(s) during the 40 days. It's not that long of a time.
I, personally, find it a wonderful tool for going from lovers to friends. (and the last one I successfully completed, resulted in wonderful friendship for 6 years, and now he's back ~ as FirstBoyFriend)(I wasn't successful at it with CurrentBoyFriend and he is, obviously still boyfriend)