Certain errors of judgement are so severe they deserve a public health warning. Never tell the unvarnished truth when your wife, or significant other, asks whether her "bum looks big in this". Never treat the taxmanto your version of Michael McIntyre's only joke.
And never, ever, if you are a Test bowler, offer Alastair Cook three opportunities to build an innings. Kemar Roach tried that yesterday, and was extremely fortunate to survive the sort of ordeal which turns otherwise sane sportsmen into a sweat bubble, or a candidate for the psychiatrist's couch.
Cook is England's first Tantric cricketer. He can go on for hours without being bored, challenged or replete. This is a man who reflects, in the Trent Bridge programme, that "only in cricket could you score 294 and still be slightly disappointed".
Well, he scored 270 lessyesterday, and will be flaying himself alive. Unlike Andrew Strauss, his captain and opening partner, he squandered a rare opportunity to profit from ideal batting conditions.
The psychodrama began when Cook, on one, nibbled at an angled Roach delivery outside his off stump. Wicketkeeper Denesh Ramdin took a superb one-handed catch, and the batsman walked towards the Victorian pavilion.
Everyone assumed that was that. But, these days, it is wise to leap to conclusions only if the stumps are atomised. Cook waited for the TV replay to see that umpire Aleem Dar had missed the no-ball. The game within the game was under way.
That was Roach's 20th no-ball of the series. His next followed just after lunch when Cook, on 12, gave Ramdin a more straightforward catch. Roach's front foot was so far over the popping crease it landed in Leicester.
At about this time he regretted it was fancy dress day. King Arthur's Knights were drinking themselves under the Round Table at the Scoreboard bar beside the Fox Road stand. Robin's men were exceedingly merry and joined them in a derisive chorus.
Roach's 13-pace run-up became palsied, as if he was tap dancing through a minefield. His direction suffered because of the disconnect between his brain and his feet, and he was not helped when Dar made great play of sweeping the crease clean.
Captain Darren Sammy noticed his discomfort and dashed from the slips to offer consoling words. When encouragement failed to free the neurological traffic jam, Sammy put himself on to bowl, and promised his crestfallen quickie a go from the other end.
All very laudable, sensitive, and utterly futile. Much to the delight of assorted furry animals in the sun-drenched stands, Roach kept the extras ticking over, and was taken off after only three overs from the Pavilion end. His meltdown concluded with a bouncer which sped for four byes.
Against all expectation, Cook nicked a quicker ball from Ravi Rampaul to Ramdin. He was mortified, especially as the left-armer is one of those West Indian players who might care to consider a trip to a celebrity fat camp.
Sammy deserved every break he received on the day he made the most eloquent statement of his career. His first Test century was confirmation of his character. The standing ovation in hishonour was heartfelt, anduniversally observed.
The West Indians are being treated with a generosity of spirit they rarely showed in the halcyon days of Holding, Richards & Co. Coach Ottis Gibson and Sammy are winning friends, if not influencing too many people, by trying to develop a Caribbean version of England's corporate culture.
They want brand ambassadors, rather than boogie children.
It doesn't make for a quiet life. You don't learn to deal with someone like Marlon Samuels, the other West Indian centurion in this Test, on the sort of leadership course where Tarquin thinks it is a good idea for everyone to conquer their inner fears by walking over red-hot coals.
Samuels obviously thinks he is as cool as a three-sweater County Championship day in April. He'd be laidback in a landslide, but could provoke a riot in a seminary. Get his head in gear, and you have a player on your hands.
West Indies might have a team on their hands if they complete the culture shift. Roach came back on as the shadows lengthened and began the long process of rehabilitation. He faces a difficult day in the field today, when goodwill will evaporate in the heat of our sudden summer.