Can you ever be friends with an ex?

Break-ups are tough - you suddenly lose the person you shared everything with. But staying friends with an ex can be equally as painful.

"I don't have many friends who are friends with their exes, actually," says Olivia Petter, author of dating handbook Millennial Love. But she has managed it in a couple of cases.

Here are the four questions you should ask before deciding whether to stay friends or go no contact.

"There are one or two men I've had brief, casual romantic relationships with that have evolved into friendships," Olivia told BBC Radio 4's Woman's Hour.

"The fact that we've 'gone there', so to speak, makes it easier for us to have close friendships without any lingering tensions or question marks," she says.

But when it comes to serious relationships, she says while she's on good terms with them they're not close friends.

Dating and relationship coach Kate Mansfield says casual relationships often have less serious life stuff to untangle, so the transition into friendship can be smoother.

But occasionally, casual relationships can trigger bigger emotions because they are "often much more intense," she says.

"It depends really on the way it ended, and who ended it, was it a mutual fizzle, or did one person decide it was over? This has more of an impact than time invested in itself," says Kate.

One of the biggest obstacles is whether you are able to separate the romance from the person.

"You need to have processed the break-up, not just moved on logistically, but emotionally," Kate says.

Consider whether you have enough in common outside of a relationship, such as genuine interests that existed independently of romance, she says. If the relationship was built entirely on attraction, it will be much harder to continue it.

It's also important to be honest about why you want to remain friends.

"If you're still hoping they'll change their mind, or if you're staying connected to monitor their dating life, that's attachment masquerading as friendship," says Kate.

In the end, staying friends only works if both people have truly accepted the end of the relationship, and neither has an ulterior motive, she adds.

3. How much time has passed?

It can be tricky to transition immediately from lovers to friends.

"It's important to have a little reset and to take some space away to reflect," Olivia says.

Comedian and author Rosie Wilby says she's been able to maintain successful friendships with her ex-girlfriends.

She and her ex Donna broke up just after Rosie's mother had died and they lost all their possessions in a house fire.

She says they only ever went no contact for about three weeks.

"That was probably about all we managed, because we had this close bond and we needed each other," she says.

Now 25 years later: "Donna feels like a sister to me," she says.

4. Is your new partner ok with it?

If you do decide to stay friends, then Kate says you need to talk openly about what you are both going to do if the other gets into a new relationship.

And if a new partner is uncomfortable with the friendship, Kate stresses you should take their concerns seriously.

"It's not always insecurity; sometimes it's a legitimate concern," she says.

You may need to have a conversation with your ex to adjust the friendship which could be "less frequent contact, more group settings, or being more transparent about what you're doing together," she says.

Olivia says women are conditioned to see male partners' exes as threats.

But Rosie says in LGBT communities, it's more common to stay friends with an ex.

"There's a completely different code of conduct," she says.

Kate says there are cases when a friendship isn't possible; if the situation is abusive, emotionally or physically, there has been broken trust or one person is still romantically involved.

"Sometimes the kindest thing you can do for both of you is to accept that this chapter is closed," she says.

Olivia says: "The only people I've cut off complete contact with are those who've caused me more serious harm in one way or another."

She says most of her friends are not in touch with exes.

"I think there's an attitude of leaving the past in the past."