The key was experience and the confidence that comes from winning regularly. By not panicking during and after a period of extremely loose play, Ireland were able to think and act their way through this one.
As O'Sullivan rightly pointed out in the aftermath, you can fix the problems that Ireland had pretty quickly (poor kicking, protection of the ball, the odd scrum being turned, injudicious decision-making) but it takes a long time to develop the ability to win a tight match when you're not playing particularly well.
In fairness, there was little comparison between what Ireland were at in the first half of that match especially and the Autumn win over Australia. Where Ireland had the confidence to retain possession from deep and trust their ability to recycle and take Australia on with ball in hand, there was a marked departure from that script on Sunday.
There may have been an element of recognition amongst the Ireland team that the level of intensity in a 6 Nations match in the cauldron that is the Millennium Stadium is of a different order to an Autumn international. The strategy may have been to play a more territory oriented game in order to keep the crowd quiet through the first quarter.
Funnily enough, Ireland achieved that objective reasonably well through the bonus of Rory Best's first minute score and by holding the upper hand for most of the first fifteen minutes.
It all went a bit pear-shaped thereafter until half-time as the decisions to kick away possession and, more gallingly, the standard of kicking itself gave the impetus to Wales. Time and again, the ball fell short of its intended target.
My mind went back repeatedly to Geordan Murphy's article in the Sunday Times in which he noted that 'the Welsh use the ERC ball. I can't say I'm a fan. I don't care what Gavin Henson says in the ads, it's very unforgiving.'
Apposite words, as events transpired. The harder the players were trying to kick it, the worse their timing was and as, Geordan put it, the ball was very unforgiving. The saving grace was that it didn't affect O'Gara's place kicking. His two conversions from the right hand touchline were exquisite. Had he drawn a line on the intended flight of the ball on both occasions, he couldn't have improved upon them. He started them a fraction inside the right hand post allowing for a tiny bit of draw on both occasions.
O'Gara personified the game. Ropey in the first half, he had the mental capacity to address his performance and change what was going wrong. Some have written that the turning point for his performance was that extremely kind bounce into the corner late in the first half. I tend to think that had he not had that lucky bounce, he would have gone on to address his performance regardless.
That he went on to make a scything break and score the clinching try was his reward for displaying that mental strength. One of the things that he displayed upon his arrival into the Irish team in 2001, along with Peter Stringer, was a tremendous mental positivity. It radiated from the two of them and was as welcome as buds in Spring.
In recent times, O'Gara has exuded this still further to a degree of bullishness and confidence that represents a significant departure from our cultural background. This team, with O'Gara in the van, is dragging us along with it into a new way of thinking about ourselves and our mental approach to sport and our sports people.
Having said all that, I would have preferred it if he had loosened his hand on the tiller in the second half still more and allowed Ireland to play more of the ball in hand game that ultimately gave us the win.
The remainder of the weekend has seen France and England lay down serious markers. This will have the beneficial effect of reducing some of the pressure on Ireland to produce a Grand Slam. For while the players might laudably adopt a 'bring it on and let's see how we perform under that kind of pressure' attitude, nobody is truly immune to the weight of public expectation. Witness New Zealand in the last four World Cups. And that was surely a factor in Ireland's seeming inability to take the game to Wales.
Our immediate opponents, France, won't have learned too much about themselves against Italy. In that sense, Ireland enter the match that bit more battle-hardened. The future of several trees are threatened by the Brian O'Driscoll, and to a lesser extent, Gordon D'Arcy, injury situations. I'll be surprised if the dynamic duo don't start the game.
Geordan Murphy is also likely to start, whether due to injury or otherwise. What a cameo he produced, perhaps spurred on by a sense of grievance at not getting the initial nod. Likewise, Rory Best may find himself giving way to Jerry Flannery. If Jonny Wilkinson can do that on 40 minutes of rugby then surely Flannery has enough in the tank by now!
It's going to be an interesting and historic week. Let's just hope that in a week where a lot of historical ghosts are being laid to rest, it doesn't turn out to be 'The Year of the French'.