London- Alastair Cook said he could no longer give the "100 percent" required as he explained in detail Tuesday why he had resigned as England's Test captain.
The 32-year-old opening batsman, who wants to continue his England career, announced Monday he was resigning after a national record 59 Tests in charge.
Cook looked emotionally drained after England's 4-0 series loss in India in December, with the tourists suffering innings defeats in the last two matches.
That followed a maiden Test defeat by Bangladesh earlier in the tour and Cook said now was the time for him to end a career as full-time England captain that started in 2012.
"It was an incredibly tough decision to make," Cook told Sky Sports at Lord's in his first interview since resigning.
"I've loved every minute as England captain, but it's a job you have to commit 100 percent to, and there have been certain times throughout my four or five years in the job when I've been to the well and dug pretty deep.
"And coming back from India, the way I felt then, I didn't think I had it in me to do it again, because this isn't a job where you can operate at 95 percent.
"When I looked in that mirror, I felt it was time. It was sad in one way, because I've loved the honour and prestige of all of it."
Cook's captaincy career included several notable achievements, including making three hundreds as he led England to their first series win in India in 28 years during his first series as full-time skipper in 2012.
England's leading scorer in Tests with 11,057 runs, Cook also oversaw last year's triumph in South Africa as well as home Ashes campaign wins in 2013 and 2015.
But in between those Ashes successes came a chastening 5-0 series whitewash in Australia in 2013/14 and the fall-out from the effective sacking of star batsman Kevin Pietersen that followed.
Although he was far from alone in making the decision, it was Cook who was the public face of a move that left him in the firing line during a 2014 home season that started with a shock series defeat by Sri Lanka.
"I think we all have regrets over how it was handled," Essex left-hander Cook said of Pietersen's departure from the England scene.
"I was part of that decision, I wasn't the be-all-and-end-all of it, but what followed was part of the responsibility I had as England captain.
"The fallout wasn't great for English cricket, we were in the headlines for the wrong reasons."
Cook, however, said his morale had received a huge boost when, following England's defeat against India at Lord's in the second Test of the 2014 series, he was cheered at Southampton before making 95 on the first day of the third Test.
England won that match and eventually took the series 3-1.
"I'll never forget Southampton, the warmth I had there in 2014," Cook said.
"That kept me going, and of course my family and friends who mean the world to me and stuck with me through the tough times."
England's next Test is not until their July 6 opener at home to South Africa.
They also have a home series against the West Indies before heading off on an Ashes tour of Australia.
Asked if he had any tips for his successor, with current vice-captain Joe Root the favourite to take over, Cook said he should use the advice of those around him.
"There are a lot of great people out there who watch a lot of cricket who know probably more than you do. So use that advice and be open to it.
"Ultimately you have to make the decision out there yourself, but use as much as you can."
He added: "I look forward to the next part of my career, supporting the next guy as best I can, and hopefully scoring some runs as well and being part of England's success."