Perhaps he was the right man at the wrong time; the one who got away; or maybe you simply split up over a trivial misunderstanding and were both too stubborn to apologise back then. But now he's reappeared in your life and those old emotions are beginning to stir once more.
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So should you follow your heart and rekindle the relationship? Possibly. First, however, you need to stop and ask yourself a few tough questions.
'Be honest,' says psychotherapist Charlotte Dunsby-Ferguson. 'Is the idea of getting back with your ex a hopeful fantasy? Or have you come to some kind of realisation about what love truly is and how good that past partnership could have been had you known then what you know now?'
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When to say no
Remember, there are plenty of 'red herring' reasons why you may feel tempted to fall back into the arms of an ex.
There's the familiarity factor, for example. You already know one another; you know each other's likes and dislikes; you don't have to start again from square one. By the same token, getting back with an ex may also seem like a convenient way to bounce back from a break-up or simply an easy way to enjoy some intimacy.
If an ex happens to pop back into your life when your current romance is on the rocks, it can feel like fate. But be cautious, warns Dunsby-Ferguson: 'Being in a dysfunctional relationship can make people look back at past loves with rose-tinted glasses. Nowadays, social media also allows the fantasy of rekindling an old romance to become a reality.
'But it's important to ask yourself whether you really want to grow and work on a potential relationship again, or whether you're simply lonely and hankering after a partner. Part of the post-break-up healing process involves getting to grips with being alone. If you haven't experienced single life and learnt this fundamental lesson, you're almost certainly considering getting back with your ex for the wrong reasons.'
Jealousy is another common trigger that can trick us into seeing an ex-partner in another light.
Perhaps you weren't overly bothered when your romance came to an end – but now he's started to see someone new, and you're beginning to question why you let him go. Three words of advice? Don't go there.
It's perfectly normal to feel jealous for a time – but, more often than not, these feelings will soon pass. There's no sense in getting back together simply because you don't like the thought of him being with anyone else.
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How to make things work
However, if you're convinced your motives for getting back together are sound – and your ex appears to feel the same way – it's time to have 'the talk'. And that means facing up to what went wrong last time.
'Things will only work out this time round if you're able to communicate honestly with one another,' says Dunsby-Ferguson. 'Otherwise, the original issues that drove you apart will eventually come up again. But to redress the balance, it's also a good idea to talk about what you've missed about one another.'
So can you ever truly wipe the slate clean and start again? Or are those old arguments destined to rear their heads again at some point? Not necessarily. The trick, according to Dunsby-Ferguson, is to make a commitment to 'grow' in the relationship. 'Getting back together can hurl you right back into the honeymoon phase, where everything is perfect,' she explains. 'But it's important to be realistic in order to avoid falling back into old behaviour patterns and repeating the same mistakes.'
Ultimately, if you're rekindling an old romance for the right reasons, there's every chance it will work out far better than it did before.
We all know couples who, for whatever reason, didn't quite stay the course first time around – but are now back together and stronger than ever. 'Couples often come back with more hope, experience and determination to make it work,' says Dunsby-Ferguson. 'Now you can compare what you initially had together to other relationships you've had since, and savour the chance to get it right this time.'
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