If you’ve been dating around for long enough, you probably have that one ex in your life. You know, the one who keeps resurfacing even after time has passed and you’ve dated other people. The idea of getting back together with this ex can be romantic. Very Romeo and Juliet-esque. But sometimes the reality is less Romeo and Juliet and more Russell and Katy — just a really bad match.

How can you decide if a reunion is a good idea or a bad, bad choice? Let these celebrity couples and their famous reconciliations be your guide: 

The Good: Pink and Carey Hart. It was a sad day when Pink and Carey Hart announced their separation back in 2008. But in the statement she released to MTV on that fateful day, Pink said, “One never knows the future, but mine and Carey’s just might involve beach babies and sunshine one day. Just not right now.” Clearly Pink had a sense that the couple’s story may not be over just yet. She explained that the relationship hadn’t ended due to cheating or anger, and wrote about how great Carey was. This was not your typical insult-slinging breakup.

What we can learn: A relationship that ends on a good note leaves potential for reconciliation. A relationship that ends because of cheating, jealousy, or a difference in values makes a reconciliation a questionable choice. Take a look at how things ended the first time around. If the relationship ended because you were arguing over stupid things, then some time apart may find you in a place where you’re ready to argue less and enjoy each other more. But if you broke up because someone was jealous or super clingy, getting back together is probably not a good idea unless something major has changed.

Honorable mentions in this category: Prince William and Kate Middleton, Justin Timberlake and Jessica Biel

The Questionable: Kristin and Jay. When Jay Cutler broke up with Kristin Cavallari just months before their wedding, it was a serious “ouch” moment. Especially when a magazine spread featuring her modeling wedding dresses was released just as they announced their split. Therefore, many people were surprised when Jay showed up at Kristin’s Dancing with the Stars performances a few months later. And they were even more surprised when the pair announced their reconciliation, and later their engagement…. and then Kristin’s pregnancy. Talk about going from 0 to 60. Guess they’re not “done-zo” anymore.

What we can learn: Take it slow. Getting back together is great, but do you really need to get back together, get matching tattoos, and then move in together? Maybe not. Take your time easing back into the relationship. A breakup can cause hurt feelings and lack of trust, particularly if one person initiated the split. Make sure you’re both feeling comfortable in the newly rekindled romance. Also, be sure that the issues that caused the first split are history. It’s great to feel like your relationship is better than ever, but there’s no need to rush things the second time around.

Honorable mention: Kim and Reggie (possibly?)

The Bad: Kat Von D and Jesse James. At first it seemed as though these two were a match made in tattooed heaven. We were still mad at him for what he did to Sandra Bullock, but in a way the Kat Von D pairing made sense. So when these two announced their engagement, we weren’t surprised. But they split before they could decide on skeleton centerpieces. They blamed it on distance. But apparently miles couldn’t keep them apart for too long because they soon got back together…. and then broke up again as Kat went public with an allegation that Jesse cheated on with her 19 women. How very Tiger Woods of him.

What we can learn: Your relationship is probably very different from Kat and Jesse. I hope. But there are lessons to be learned from these two crazy kids. Even if you have similar interests, values (possibly lack thereof) or tastes, it doesn’t necessarily mean that you’re soulmates. Also, relationships that start when someone is on the rebound are usually not promising. And, for the most part, once a cheater always a cheater.

Honorable mention: Brooke Mueller and Charlie Sheen

Before you get back together with your ex, try to put on your own personal Sorting Hat and figure out where exactly your relationship falls. Are you of the Pink and Carey Hart variety where you ended on good terms and needed time apart to realize how much you appreciate each other? Or are you more Kristin and Jay where you have the potential to work again but need to take it slow? This is good, but make sure you’ve worked through past issues, aren’t rushing things, and are getting back together without emotional baggage. If you think you’re like Jesse James and Kat Von D, then getting back together should probably be avoided.

Have you gotten back together with an ex before? Was it a great choice or a disaster?