Boreham Wood manager Ian Allinson has resigned, saying the National League club's move from evening training to a daytime schedule is a major factor.
The former Arsenal winger took Wood to the top flight of non-league football last season with a Conference South play-off final victory over Whitehawk.
But the 58-year-old, who also works in the alcohol industry, says he now cannot commit fully to the job.
"This is a decision that I haven't taken lightly," said Allinson.
"I have thought long and hard about this over the last few weeks before coming to the realisation that the new training schedule wasn't allowing me to manage the team to the level of my expectations."
Allinson, who first went into management with Baldock Town in 1989, took charge of Boreham Wood in May 2008 following the exit of Steve Cook.
He leaves Wood 20th in the National League, one place and two points above the relegation zone.
"This is not a retirement, I still have plenty of fight in me and want to carry on with new challenges and hope to continue the success I have had over the last 25 years as a manager," he said.
"I am extremely proud of what I have achieved in the past seven-and-a-half years at Boreham Wood.
"When I took over the club for the second time, they had just been relegated to the Ryman North Division before being given a reprieve.
"I would like to go on record to personally thank the chairman Danny Hunter for not only his support as a chairman but also as a very close friend. I am sure this friendship will continue for many years to come."