What makes a young, successful, manager like Zinedine Zidane walk away from Real Madrid, as the Frenchman did this week after just two and a half years in the job?
It is almost certainly the relentless pressure of constantly chasing success at a club competing with Spanish rivals Barcelona for not only domestic, but global domination.
Pressure cooker club
At Real Madrid, no-one is allowed to take their foot off the pedal. When you have been European champions 13 times, trophies are quickly forgotten, creating a constant state of stress which led Zidane to resign after less than three years in the job. He opted to walk away while still basking in the glory of his third consecutive Champions League title, saying he feared failing next season.
"It wears away at you here," he said on Thursday.
Zidane said the low point of his coaching career at the club was being knocked out of the Copa del Rey, Spain's cup competition, in January by modest Leganes. He faced intense criticism at the time.
"There are difficult times, when you ask yourself: 'Am I still the right person for the job?'" he said.
Having shone in the Madrid shirt as a player in a five-year stint from 2001 to 2006, Zidane took the job of coach knowing full well that no Real manager in the 21st century has lasted more than three and a half years in the job.
"No material is more combustible than Real Madrid, and it is always exposed to fire," sports newspaper Marca said on Friday.
Training sessions, team meetings, matches, post-match press conferences, warm-down, training - at Real the coach is always juggling tasks in a packed day with the glare of the media on him.
It might explain why Zidane often appeared at press conferences seeming happy but somehow empty, even blank-faced.
"Living every year like that, with so many competitions, so many matches and so much travel, it can be enormously wearing," Alfonso Perez, who played for both Real (1991-1995) and Barcelona (2000-2002), told AFP.
"When you go into a club like that, you know what you are letting yourself in for. There is enormous pressure and you have to do well. It's like an exam, 24 hours a day," the former Spanish international striker said.
Pep Guardiola and Luis Enrique complained of the same pressure when they managed Barcelona and both stayed no longer than four years in the job. "It takes its toll in the end," Guardiola said.
The fussiest fans
At Real, as at Barca, failure to win quickly escalates. One winless match is an accident. Two create doubt. Three are a crisis.
The fans at the Santiago Bernabeu are among the fussiest in the world: they want beautiful football, victories and trophies and do not hesitate to boo their own players.
"We had difficult moments during the season, when there were whistles." Zidane said. "They are demanding fans."
The club with the second highest revenue in the world and the most international trophies is scrutinised relentlessly by the Madrid, the Spanish and the global media in a never-ending frenzy that Real Madrid help to foster.
As one controversy chases another, it must be tiring to answer over and over again the same questions about Cristiano Ronaldo, Gareth Bale and Real's possible interest in Neymar.
Time to rebuild
The Real squad, with its huge egos and repeated sulks, seems difficult to manage. Yet Zidane eked the best out of Ronaldo, restored the confidence of the unloved Karim Benzema and provoked some of the underperforming dilettantes to produce.
The squad has aged and needs rebuilding. After delivering three straight Champions League titles and building a nice war chest with his parsimonious transfer spending, Zidane is leaving that high-stakes, high-risk gambling on talent, to someone else.