I was talking to a friend the other day that had just come face to face with her boyfriend's ex-girlfriend and since her man and his ex were together for a couple of years, she was understandably feeling a little uncomfortable about the whole situation - especially since the two of them still share the same friends and social activities and seem to get on very well.
I tried pointing out that an ex is an ex for a reason so she shouldn't worry about it too much. If they couldn't make it work after two years together then the likelihood of them getting back together and making a go of it was very slim.
The fact of the matter is that her situation isn't unique. It's how you deal with it that will largely determine whether or not you and your man/ woman will make it through or not.
The first thing to bear in mind is that being insanely jealous isn't going to help the situation. You may not be able to control how you feel, but you can control other people's perception and your best bet is to act as if it doesn't bother you.
Fake it 'til you make it. Even if they never mention it, your partner will notice and be impressed.
It's never easy coming face to face with an ex and they'll be really grateful to you for not making the situation any worse - and you'll even gain brownie points for seeming relaxed and confident in a potentially volatile situation. It will also help cement in their mind why they like you in the first place. And besides, if the ex seems to be a little too flirty with your partner, it will unsettle them when they realise you're not worried about it.
More often than not, bumping into the ex will only be a one-off situation but if, like in this case, it's likely to happen on a regular basis you need to put your mind at ease about the situation. While it's usually not a good idea to talk about ex-partners with a current lover, doing so is a good idea in this situation.
Sit down with your partner and casually and calmly discuss the conditions of their break-up.
If you partner is a reasonable person, they'll totally understand. If they don't, then you might want to think twice about whether or not they're worth the hassle in the first place.
If the situations get difficult to deal with and your partner and their ex look too cosy for comfort it's time to put your foot down but once again be calm and relaxed about it, your partner might not realise that it's not appropriate now that you two are together.
Gently point out that their constant giggling and sharing of private jokes makes you a little uncomfortable and then leave it to them to deal with the situation. Whatever you do, don't get into a confrontation with the ex.
It's far better to sit back and let your partner know you trust them to do what's right. Either they'll sort it out or they won't, in which case it's probably not completely over between them and you're better of knowing it now.
Whatever happens, it's important to keep a healthy balance in your relationship. Never accept second best but it's also important not to expect them to drop every aspect of their life for you. As the proverbial 'they' say: "Keep your friends close and your enemies closer".