NICK Crews, 67, was captain of a nuclear submarine before his retirement. How appropriate then, when he'd had enough of his grown-up children, that he should choose the nuclear option.

Last February, he sent an excoriating email to his three children, in which he vented his ''bitter disappointment'' with their ''copulation-driven'' self-indulgence. Despite his providing them with the best schooling and a solid home background, the three had failed to succeed at either work or marriage. Crews and his wife cherished their six grandchildren, but worried that ''these lovely little people'' were suffering because of their parents' ''underachievement and ineptitude''.

Not surprisingly, the ''Crews missile'' has caused a storm. His educated son Fred, who works for a taxi firm, has been getting his own back by telling the newspapers that he and his sisters were nothing if not the product of their upbringing. In other words, if they were monsters, Nick Crews was the guilty Frankenstein.

The naval captain's electronic kick up the backside has sent ripples well beyond his family. Many parents with grown-up (and not so grown-up) children have been expressing their sympathy. Tolstoy may have written that every unhappy family is unhappy in its own way, but the broadside from this paterfamilias strikes a chord with the great majority in the squeezed middle-aged middle classes. Parents like the Crews have given up a lot for their children. They have paid for private schooling, university, mind-improving holidays, expensive hobbies or all of the above. It comes at a big cost.

Many mothers and fathers have worked long and hard, and when even that didn't raise enough, they have gone cap-in-hand to the bank manager or to their own parents. Many will have forfeited personal satisfaction for their children's sake. They have drunk cheap plonk, or none at all. They have worn shabby clothes and driven rickety cars. They have postponed paying off the mortgage and failed to build up the pension pots they needed. They may have turned down an interesting job that would have meant a lower salary and stuck to a no-longer-thrilling marriage to give the children a secure home.

Their unselfish aim is to ensure that the next generation has the best possible start in life. But when that start proves to be not a springboard to success but a mattress to snooze on, who can help getting as cross as Crews?

Sacrificing ourselves for the children's welfare is rewarding. But when it is taken for granted it can easily lead to resentment in us. Worse, it leads to self-indulgence in them.

Mollycoddling robs young people of self-discipline and ambition.

Like Captain Crews, many parents despair of their children's emotional incontinence as much as their professional fecklessness.

Adult children's emotional neediness is a sad descent for those reared on the principle of self-reliance. Bad enough to make a mess of your life.

Worse still to expect others always to pick up the pieces. This is the sponge mentality: soaking up every benefit (state or family) that is going, while dribbling out every woe to Facebook ''friends'' and Skype confidants.

Much modern thinking about parenting encourages this sort of attitude. Self-help books, parenting ''gurus'' and websites are unanimous: parents should be child-centred. This entails baby-proofing homes, with padlocks on cupboards and stair-guards on every floor; later, ensuring that the teenagers' guitar lessons and remedial French take priority over your weekend lie-in.

Today's pedagogues tell parents that they must be patient, letting their offspring unburden themselves and take years, not months, to discover their ambitions.

The right-thinking middle classes pay lip service to this attitude. I still remember the shocked looks we earned at the playground when, as our toddler tottered up a climbing frame, my husband barked in mock ferocity: ''Don't you dare fall! You know that daddy only likes winners!'' If my husband had been sporting a dirty raincoat, a bag of sweets and a beckoning finger, the other parents could not have been more horrified. They backed away, clasping their children and tut-tutting at this dreadful display of parental pushiness.

The attitude that my husband was mocking has become daily reality for many. They may seem non-judgmental and supportive, but these parents inflict the most ferocious (if covert) competitive pressure on their children. They are the ones who pack every after-school minute with activities designed to give their children a leg-up, whether it's Kumon maths drills, ballet, Mandarin classes or all of the above. They are the ones who pilot children through the top schools' open days, and hover menacingly during exams prep.

These parents fear their children's every mistake because it reflects badly on them. I can't help wonder, though I find the Crews children infuriating, whether this is what Fred was trying to express with his obvious rebellion: he and his sisters did not join the navy, or get the right job, or seek to be a carbon copy of their parents. Maybe the siblings sensed mum and dad were not so much genuinely rooting for them as hoping that the children's mistakes wouldn't show up the parents.

Many adults go through life in the shadow of an ambitious father or mother, aiming to live up to their parents' investment of hope, time and cash. As long as the desire to please mum and dad lasts, it may bring results. But it is a fragile foundation for success - and happiness.

Tough love is not just about setting strict goals, as Crews obviously did. It is also about setting children loose: giving them a good start in life, but allowing them to fail as well as succeed.

Cristina Odone is a novelist and a columnist with The Daily Telegraph, London.