What, one wonders, will Debrett’s new etiquette guide to divorce recommend?

“Don’t throw diamonds after 6pm”? “Never wear white to a custody hearing”?

“When communicating only through venomous notes, a titled husband must be addressed as ‘Dear Lying Sh*t’, never ‘B******’”? “Never stay together for the sake of the estate – you’ll only make your gardener unhappy”? One, of course, hopes. But one would be disappointed.

Vexingly, it is only the stereotype of Debrett’s as the record of a fragile mesh of arcane conventions that still hangs together in our folk memory, as ancient and delicate as a Victorian lace collar, that is good for a laugh. In reality, the latest volume is a sensible, practical tome which promotes old-fashioned good manners – which is to say, the prioritisation of self-control over self-indulgence in all circumstances, including the most trying.

One of my friends damned the book because “divorce is the one time you’re allowed to go a bit mental”. No. This is exactly what’s wrong with a) her and b) people. Divorce is terrible. It’s like a bereavement – the death of love, of many people’s hopes and dreams – not just the couple’s but their parents’, siblings’ and friends’ for them – and of years of future happiness together, whatever new relationships may happen later. And once children are involved, you can add their misery, uncertainty and the infinite multiplication of guilty feelings within the breasts of their begetters. It’s awful. Awful.

But even here – especially here – stoicism will always serve you better than weeping, wailing and wallowing. And it will serve those around you better still.

Manners (if we leave aside sh*twittery about fish knives and napkin’ vs ‘serviette’ usage) are about maintaining the orderly working of society, greasing the proliferating number of wheels involved in every transaction and interaction once you’re dealing with any gathering larger or more complex than one peasant kicking around his sod hut. Just as any friendship group can only cope with one drama queen – the ratio of time/booze/emotional support to diva entertainment value being too high to allow more – society can only support so much piggishness among its members. Otherwise the whole stately gavotte in which we weave in and out of each others’ lives collapses in chaos.

And manners are sliding further and further from our grasp. We know this and we mind this. This is why attempts are often made to impose mannerliness in public places – this morning I heard an announcement on the train exhorting everyone to keep their feet off the seats and “use mobile phones and headphones with consideration to others” (this should, of course, be “for others” but it would be unmannerly to point that out). It’s a recognition that life is better for all when everyone gives up a little of their own comfort. Any train trip will illustrate just how toxic bad manners are – one tiny, tinny percussive beat issuing from the headphones of a single individual can ruin the journey for the entire carriage; 20, 30, 40 people wordlessly but profoundly irritated by the disrespect shown to them by another human being and then carrying that discontent with them and taking it out, in a 100 tiny ways, on others. All because one cretin can’t turn the volume down a notch.

I’m sorry, where was I? Oh yes. The point is that everything works best when we indulge ourselves least. Not wasting your energy on histrionics – as distinct from the expression of genuine unendurable misery – during a divorce means you have plenty to spare for yourself and your friends have plenty to spare for you when said unendurable misery starts hurtling, as it surely will, towards you. Not maximising your comfort at the expense of others’ leaves lots of goodwill in the collective bank for us all to draw on in the future. It’s a formula that works for anything at any level, from personal savings (don’t spend it all as you earn it and you’ll be happier in the long run) to the global environment (don’t reduce the Earth to a spinning ball of dust and you’ll be even happier in the long run).

And if you can use the right knife as you go – why, that’s even better and I drop in a curtsey at your doubtless suitably-shod- for-any-occasion feet as you pass.

Contact Lucy Mangan at lucy.mangan@stylist.co.uk; twitter.com/lucymangan

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