Alastair Cook says he did not have the energy required to stop the England team from "stagnating".
Cook stepped down as skipper this week after captaining England to an unrivalled 59 Tests.
The national side's record run-scorer took almost six weeks after England's 4-0 defeat in India to confirm his decision to step aside, but concedes that deep down he knew his time was up once they lost the final Test in Chennai by an innings and 75 runs.
At The Oval only six months ago, England were within one more win of going top of the ICC's Test rankings.
They had already endured a patchy 2016, however, and after losing for the first time to Bangladesh and then journeying on without success to India, their eight Test defeats in a calendar year equalled an unwelcome national record.
"We've kind of stagnated if we are being brutally honest," said Cook. "There is a lot of work to be done and I felt I just didn't have that energy to do it."
He added: "That's part of the parcel of being captain, you are responsible.
"The dressing room has been fantastic; the support of the players has been brilliant. It's just, I think, that hearing a new voice could help."
Cook can look back on two Ashes wins on his watch, as well as notable series successes in India in 2012 and then South Africa just last year.
His tenure has, however, been up and down, and he believed his time was up as captain, saying: "I felt, unfortunately, that I was done.
"It was sad - it's a job you need 100 per cent commitment to. But looking in the mirror at the end of India, I felt I couldn't do that. It might have been 95 per cent, but that's not good enough.
"It's not a job you hang on to like that ... I just felt the team just needed a push in a different direction."