There is wisdom in the advice of these two writers. Michel Montaigne said:
If it doesn't go along gaily and freely, it goes nowhere worth going. We say of certain words that they smell of oil and the lamp because of the certain harshness or roughness that labor imprints on productions in which it has a large part. But besides this, the anxiety to do well, and the tension of straining too intently on one's work, puts the soul on the rack, breaks it and makes it impotent; as happens with water, which because of the very pressure of its violence and abundance cannot find a way out of an open bottleneck.
Hampl writes that Montaigne (in the 1500s) developed the personal narrative essay as a "basket" of thoughts. She also has written her own book as a basket of thoughts, and in its free-ranging and leisurely pace, I contemplate my own efforts to complete a writing project. When I consider previous writing, I know that not straining is good advice. D. T. Suzuki, in the introduction to Zen in the Art of Archery writes:
Man is a thinking reed but his great works are done when he is not calculating or thinking. "Childlikeness" has to be restored with long years of training in the art of self-forgetfulness. When this is attained, man thinks yet he does not think. He thinks like the showers coming down from the sky; he thinks like the waves rolling on the ocean; he thinks like the stars illuminating the nightly heavens; he thinks like the green foliage shooting forth in the relaxing spring breeze. Indeed, he is the showers, the ocean, the stars, and the foliage.Effort that becomes forced is not good effort. If something doesn't work, it doesn't help to do it harder. One must change. Instead, one might find another angle. Relax. Stop trying to control it. Find the voice and listen more deeply. Let it go somewhere else. Pay attention.
In Hampl's words as she introduces the quote from Montaigne, "In order to be trustworthy, writing must have a chaotic charge, an unbidden quality" (p 69). This also reminds me of Richard Hugo's Triggering Town. The initial writing is simply a place to start. Hugo began his writings with a description of a town he had traveled through, and in his practice, something else emerged on the page. This second topic, unbidden, was the true subject.
To read an excellent review of Hampl's book, see https://www.npr.org/2018/04/23/604910290/art-of-the-wasted-day-makes-a-case-for-letting-the-mind-wander