It's like a bad joke -- you're with your boyfriend and spot your ex, who sees you and starts to make his way over. You begin to get anxious and look for a way out of the situation before it's too late. I've been there -- a few times, actually -- and the thoughts that run through your head at that time are likely a lot worse than what will actually happen. You don't have to plan out an entire speech, but at least have a brief idea of what you would do should the situation occur, even if you think it won't. It's better to at least consider your actions rather than get caught off guard.
Don't try hiding
I was at dinner with a friend when she started ducking behind her menu and a minute later a past partner of hers walked up to the table and said hello, then asked her if she was trying to hide from him. You'll look more ridiculous trying to hide from your ex than if you just acted normally. It also makes him think he has an effect on you and that's the last thing you probably want. Pretend you're not even phased by his presence.
Smile and be friendly
Smiling and being friendly to your ex may involve you doing so through gritted teeth, but it's worth it. The last thing you want to do is start a problem, especially in a public place, between yourself, your ex and your boyfriend. Be as friendly as possible even if you would rather kick him in the knees and run.
Introduce your guy as your boyfriend
Instead of introducing your guy only by name, precede that by saying he's your boyfriend. If you don't, he's likely going to be irritated later and think you were embarrassed to say who he is to you. However, introduce your ex only by name and not as your ex-boyfriend. You can explain to your boyfriend later who he was, but doing it at the time is only going to create extra tension.
Be the bigger, better person
Even if your ex starts running his mouth, making snarky comments or trying to bring up the past, keep the smile on your face and restrain yourself from saying anything nasty in return. Being nice will very likely irritate him much more than firing back with comments. The latter will let him know he pushed your buttons and can still get you riled up.
Don't hang all over your boyfriend
If you grab onto your boyfriend and start making out with him as your ex approaches, it's going to look like you're purposely trying to get a rise out of him. Grabbing onto your boyfriend at that moment is likely only going to have one effect -- making you look bad. Your ex will probably laugh about it and your boyfriend may get mad thinking you only did it at that moment to make your ex jealous.
Make a run for it
You don't have to stand there and have a lengthy conversation with your ex. Exchange pleasantries, then move on to someone or something else. The less time you stand there, the less of a chance there is for issues to arise or tensions to increase.
The aforementioned tips can obviously also apply to ex-girlfriends as well, however, it seems that men have more of a tendency to approach their ex's while in public than women do. Regardless of whether it's an ex-boyfriend or girlfriend, be cordial and give off the impression that you're happy and over anything that happened in the past. You'll only have to squash the anxiety and deal with your ex for a few minutes before you can move on.
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