You are your biggest enemy. You are also your biggest friend. And when you have won the battle with yourself, there is little that can stop you.
Brendon McCullum is a man whose batting has been built around the belief that cricket balls are flies to be swatted away with disproportionate brutality. For nearly two days at the Basin Reserve, he has battled this belief. He has battled what he has stood for, and what the world has known him for. He has overcome his own essence.
What it must have cost the man we will never be able to tell. For how many of us can say we have militated against our own nature and succeeded?
In overcoming his mind, he has also had to fight his creaking body, battered so much over his career that it is much older than his 32 years. He makes double-centuries, comes back to field at cover, chases balls like a terrier and dives into advertising boards at the boundary, without a care, to save a single run.
After the day's play, McCullum said that he had scraped through the final hour in a daze. Had he not told us, we would never have known. For McCullum would not let us in on the pain and self-denial while batting. Yes, he had taken treatment for his back during the day, and also had a sore shoulder. BJ Watling said his captain was carrying plenty of niggles. From the outside, however, all you could see was a captain, on 277, running hard in his twelfth hour of batting for a third run from Jimmy Neesham's bat.
Over those 12 hours, McCullum had taken denial to another level.
Sachin Tendulkar rightfully got the accolades for putting away the cover drive during his unbeaten double-hundred in Sydney in 2004. Tendulkar knew he had been getting out to that stroke, and just excluded that particular risk over a long innings.
McCullum's entire game is risky. And he rightfully gets flak for often throwing it away needlessly in trying to beat the ball to pulp. At times, the flak is uncharitable. As McCullum has gone about losing every toss this series, some have said he is not even doing the only thing he can be expected to do.
Forget the detractors, even his staunchest supporters would not have expected this kind of innings from McCullum. The Auckland double was different. India helpfully lost their lines and lengths after having New Zealand 30 for 3 and McCullum is not one to let short and wide go unpunished.
India were not giving an inch this time. Those two dropped chances will be forever associated with this innings, but had they not happened, the world would have never discovered that McCullum was capable of such renunciation for so long. There was little else.
The Indians wanted him to play strokes, as would any side. He was tempted. He was squeezed. He was set conventional and unconventional fields. He did not yield. There were plays-and-misses, you would be beaten a few times if you batted for 726 minutes. But they were the exceptions, against the run of play. He did indulge himself, and the strokes became more frequent after the first few hours, but he was never reckless.
This wasn't the McCullum we have known, resisting by attacking as hard as he can. This was a captain missing his best batsman, having lost half his side and still needing 153 to make the opposition bat again. This was a captain who did not want to let his side's glorious summer be scarred by a meltdown in the final game.
This was a captain prepared to do anything, even rebel against his own character as a batsman.
How many times must he have felt like having a whack at the spinner. How many times must he have felt like letting himself have one, just one, heave against the quicks. But the image that stays behind is of McCullum jerking his bat skywards to let one more pass outside off. Of jumping across, getting behind the line of another lifter and dead-batting it.
Virender Sehwag, a batsman similar in intent to McCullum, made two Test triple hundreds staying true to his aggression. Imagine Sehwag restraining himself to a triple. History will, of course, accord McCullum's innings the place it deserves. It is perhaps no coincidence that he ended the day unbeaten on 281, a number that - thanks to VVS Laxman - is forever associated with the impossible being achieved on a cricket field.