Their idea, strongly supported by thousands of case studies, is that to maximize success (whether in academics, tennis, the corporate world, etc.) one must practice deliberate spurts of stress followed by periods of strategic relaxation. It is easier to apply this in practice than the interesting but hardly practical content in the article. For example, for the past few hours, I've been working hard on understanding some algebraic geometry from Hartshorne, but now I'm daydreaming about neuroscience and salsa.
Thus, a perfect creative effort is a fusion of focused dedication interspersed with lackadaisical goofing around.