There have been many post-mortems on the Proteas' epic but ultimately agonising semifinal defeat to New Zealand. Rain, Duckworth-Lewis, Philander's hamstring and Abbott's exclusion, a choice between length balls and yorkers, negative bowling changes, dropped catches and botched run-outs have all been discussed, cursed and bemoaned as we contemplate another World Cup disappointment.Post-mortems, of course, benefit everyone except the dead guy, and so I don't wish to pile on my own autopsy, other than to say that firstly I'm glad we have, for the most part, not added this one to the "choker" column. And secondly, in the cold, harsh analysis that must eventually emerge from defeat, we will see that we played only four truly competitive matches at this World Cup (this excludes the weaker nations and a woeful West Indies), and we lost three of them.Given that AB de Villiers kept proclaiming that we were the best team at the tournament and would beat anyone on our day, this leaves an awkward reality that on three of the four days against competitive teams, we didn't. So, either we carried false bravado through the tournament, or we carried far too many players who didn't live up to an accurate assessment of their abilities. And yes, the whole picture might have changed had even one of perhaps five key moments gone differently, but ultimately, this was a collective underperformance - understanding why will determine our four-year prognosis.What the game did do is showcase one of sport's most appealing attributes - it is a safe environment that exposes its participants to pressures beyond that which most of us experience in our own lives, and we revel in it.Let me just emphasise, for the sake of perspective, that there are far more pressurised situations than an ultimately trivial sports event - people fight life-or-death wars, make medical decisions on which lives rest, and deal with natural disasters that have far greater bearing on people than a boundary off the last ball ever will.But sport is a safer window through which to observe the human mind grapple with fear, consequence and reward. In the 2004 Athens Olympic Games, Matt Emmons built a commanding lead in the three-position rifle competition. He'd already won the 50m prone gold, and going into the final round of the three-position event, he needed only an average score to win an historic double. He duly produced a great shot. into the wrong target, that of an adjacent competitor, and finished eighth.Four years later (you can't make this up), Emmons again went into the final round with a large lead, and needed a relatively low score to secure gold and redemption. In the process of lining up the winning shot, however, he pulled the trigger early, scored only 4.4 and fell to fourth. This is a man, recall, who won Olympic gold, broke world records and won numerous other titles. Yet in two high-pressure situations, he failed twice for no reason other than the occasion and scoreboard.Similarly, we currently enjoy three of the greatest tennis players ever to play the game. But Federer, Nadal and Djokovic also succumb to pressure in big moments.Rory McIlroy is another example - he led the first three rounds of the 2011 Masters, then shot 80 to fall from first to 15th. Charl Schwartzel was the ultimate beneficiary but McIlroy has since evolved into the best golfer of his time, with the potential to become an all-time great.The point is that pressure is often the filter that separates the good from the truly great, because it determines just how close to their potential an athlete will get. This mental aspect was once a neglected area of performance. It no longer is, but we're a long way off understanding it enough to change how players cope with it. If we ever do, perhaps it'll be the difference between the agony and ecstasy of the last week...