That, however, was only a fleeting source of regret bearing in mind the buoyant mood inside the stadium and renewed sense of optimism.
The simple act of taking a step forward, experiencing a fleeting twinge of regret, recalling an incident from the morning commute or tasting a doughnut requires millions of simultaneous and precise synaptic firing events throughout the brain and peripheral nervous system.
By far the most confident of the performers was the Peking opera star Wu Hsing-Kuo, who portrayed the Yin-Yang Master; he was a joy to watch, his face communicating shades of pain, regret, fleeting joy, and wry wit that were barely indicated in the score.
However, a loose backhand error followed by a netted forehand under pressure saw the moment pass, and Murray would regret that fleeting opportunity when Federer made the breakthrough at 5-5.
In my mind at least, there was also a fleeting, thin and unexpected sliver of regret, which I still can't fully explain: the pang of watching a hunter standing over a shot stag.
These 14 tender sketches not only snared a lifetime of love, loss and regret, but also captured moments of fleeting euphoria, raising day-to-day reality into the realm of the sublime.
After half a decade as a changed man, my only regret is that this whole moment is surely fleeting.
So we get quicksilver footwork and summery Frederick Ashton romanticism, tempered by a shiver of Antony Tudor regret, and cast in an enigmatic light by fleeting parallels to Jerome Robbins's Dances at a Gathering.
All the gifts we are offered in life (as Marías himself is fond of pointing out) are fleeting ones, easily lost or ignored or undervalued and only regretted when they are no longer available to us.
And there is hope that this Arab autumn will be a fleeting one, yet there is alarm regarding a possibly worse winter which could carry with it causes for regret and amazement.
