In Netrunner, this saying would apply to the runner moreso than the corp under most circumstances, I think.  In the beginning of the game, if the runner does not run when he can, the corporation often has an advantage in setting the tone of the game.  Running adequately early in the game could be the "normal force."  It's tricky, but most players I know, especially newbies, are prone to not running enough rather than too much.

What is the extraordinary force?  The runner, if prudent in the early game, and especially if the corp gets lazy in its defenses, can build what I call a "full icebreaking suite."  The ability to break any ice is precious, and should not be squandered.  At the point in which the runner has a full icebreaking suite and forty-odd-some bits in his pool, it is time to let loose and tear down the data forts like Chinese cannons killing the Mongols (Sun Tzu is probably turning in his grave right now ;-).

In short, at all times, be as agressive as your situation will allow you to be.

Ryan "The Gryphon" Kelly
http://www.oocities.org/TimesSquare/Ring/4745