Yes, after much bitterness and pain he's gone from your life… but then he's back to pick up the kids for Saturday sports. Or he's there, in the corner next to Sophie's birthday cake, chatting to your sister or work colleague or dear neighbour Bill.
Do you bristle? Or try your best to ignore him, hoping he'll leave as soon as the presents are opened? Maybe you're tempted to drop in a cutting remark about Tom's bicycle, which he forgot to bring round, or the music lesson bill he promised to pay half of by the end of the week.
But the bigger question is: do you want to torment yourself in the process of tormenting him, or do you want a workable relationship that puts all the old hurts behind you?
Roughly a third of marriages end in divorce, so it's important we learn how to navigate a post-breakup relationship, particularly when there are children involved.
While it might not happen to you, there's a good chance it will happen to someone within your circles – so be armed with the knowledge of how to treat an ex like a relative so you can reduce the stress.
I suggest disinterested compassion. Think of him as a relative; one who pops round more often than everyone would like. Yes, annoying on occasions but not a bad person. It's not easy to do, I admit.
Couples can't deny they have a shared history; that once they were joined by love and now they're connected only by the consequences of that love – their children. Undoubtedly, his presence will stir feelings of hurt, resentment, and sadness. And definitely awkwardness. Once they had shared the same bed, every intimate part of their lives, and now he is a stranger of sorts, so familiar and yet so distant.
His very presence makes his ex – and others – uncomfortable. Does she treat him as the enemy, a complete stranger or some recent acquaintance – pleasant but aloof? It's tempting to pretend he doesn't exist, but of course he does.
In reality the relationship hasn't ended, it's simply changed. Like it or not, they'll be connected for many years to come. Together, couples need to make decisions about care arrangements, schooling, health matters, sports, clothing, travel and general life decisions for the precious little people they've both brought into this world.
It's the children who matter most here. Clashes over the children won't go away. They exist even in the best of relationships. Each has different ideas of what a child needs to grow into a healthy, well-adjusted adult. When opinions differ, for the sake of love, peace and a happy household, concessions will have to be made.
A kind heart – or at least one filled with disinterested compassion – will be reciprocated (eventually) by kinder, more considerate actions. As I tell clients, you may not have made a success of your relationship, but you can make a success of your separation.