Alastair Cook admitted to doubting himself but never thinking about the end of his career before completing his fifth double hundred on day three of the fourth Ashes Test in Melbourne.
Cook had scored just one Test century in 2017 - an innings of 243 against Windies at Edgbaston in August - before he ended day two at the MCG unbeaten on 104, his 32nd Test ton.
The former England captain says he was "emotional" at ending a barren run of form, having headed into the Boxing Day Test with 83 runs in the Ashes series at an average of 13.83.
And he told reporters at stumps on Thursday, after ending unbeaten on 244, that he was delighted to produce an innings of substance, with the only irritation that it came after the series was lost - Australia having regained the Ashes with a thumping victory in Perth before Christmas.
Asked whether he was concerned about his struggle for runs, Cook said: "100 per cent. I have doubted myself for 12 years and will probably continue to doubt myself.
"I always feel as though I have the backing of the selectors but you still have to deliver the goods and I hadn't done that on this tour.
"[The selectors] would have been entitled [to drop me] just because I literally hadn't scored a run since Edgbaston.
"I have never thought [about my career drawing to a close], I've always thought about fighting hard and trying to put in a performance.
"The longer it goes the harder it becomes. That's why I am proud I have been able to go to the well again and put in a performance like that.
"It was probably one of the most emotional [innings] last night from where I had been on this tour. It meant a lot.
"I was then proud that I could back it up and get a real big one for the team.
"It's just a shame that it's three and a half, four weeks too late and I will have to live with that for a long time."
Cook's knock, which has lasted for over 10 and a half hours, has seen him set the new highest score by a foreign batsman in an MCG Test, eclipsing the 208 Windies' Viv Richards scored in 1984.
The 33-year-old is now up to sixth on the list of all-time Test run scorers, moving past Sri Lanka's Mahela Jayawardene (11,814) and Windies' Shiv Chanderpaul (11,867) and Brian Lara (11,953) after beginning the day in ninth place.
Wally Hammond (7) is the only batsman to have scored more double centuries for England in Tests than Cook, who is the fifth batsman to score 200 at least twice in the Ashes, having also done so in Brisbane during England's victorious 2010/11 tour.
"I've always worked hard on my whole game and my approach to cricket, so unfortunately most of my runs are pretty ugly and quite hard work," said Cook. "That hasn't changed throughout my whole career.
"There are quite a few moving parts to my game. When they're not quite in sync it can be quite frustrating. It's never going to be pretty, my batting, but sometimes it's effective."
Australia coach Darren Lehmann added: "Cook was simply brilliant.
"He batted a very long time and was more aggressive than he was in the other Tests.
"He played brilliantly and showed some of the younger guys how sometimes you've just got to tough it out."