Clarke scored an unbeaten 329 in the second Test against India here which Australia won by an innings and 68 runs.

He was widely lauded for putting team ahead of himself when he chose not to go past Sir Donald Bradman and Mark Taylor's 334 at the SCG and declare the innings after Australia took a lead of over 400.

"It would have been a very hollow feeling to score so many runs and not win the Test. I can vividly recall that hollow feeling in South Africa just two months ago," Clarke wrote in his column for 'The Daily Telegraph'.

"The 151 I made in Cape Town was probably my best Test innings given the conditions were so heavily in favour of the bowlers and the quality of South Africa's pace attack," he recalled.

But that aside, Clarke said he still can't believe he went past 300, that too on his home ground.

"I still can't believe I have scored 300 runs in a Test. It hasn't sunk in and I don't think it really will until I retire and look back on my career," he said.

"I think that's the same with any player. You live in the moment, concentrating on the next ball you have to face or the next Test you have to play. There is little time for reflection. And the only reason you score runs or take wickets is to win games," he explained.

"So I never let myself get carried away with my score at the SCG last week. It was all about scoring enough runs quickly enough to win the Test and go 2-0 up in the series after our strong performance in Melbourne."

The 30-year-old Clarke said the jubilation he displayed on reaching 300 was meant to thank his family and friends for standing by him during periods of upheaval in his life.

"The emotion I displayed reaching 300 was not because I had managed the rare opportunity to make such a big score. It was a big thank you to my family and friends for all the support they have given me over the years," he said.

"We have been though a lot as a family and I have had my ups and downs as a cricketer so to be able to repay their faith in this way makes it very special.

"There is nothing more satisfying as an Australian cricketer when you reach an important milestone than to raise your bat and see your team mates on their feet applauding and your family and friends in the crowd doing the same," he added.

Explaining the reasons for declaring just five short of Taylor and Bradman's record, Clarke said it was pre-decided that the declaration would come as soon as Australia took a lead of over 400.

"Just when I declared had nothing to do with my score. It didn't matter if I was 250 or 300 or 400, I wanted a lead of at least 400 with plenty of time to bowl India out on what had quickly become a very flat wicket," he said.

Clarke said he wanted Michael Hussey to get to 150 as the senior batsman had played exceptionally well.