DFW is perfect towards the end, when he talks about acceptance and awareness— the thesis ("This is water") is spot on. But the way he approaches it, as a question of choosing what to think, is fundamentally, tragically wrong.
To Mindfulness-Based Cognitive Therapy folks call that focusing on cognition rather than experience. It's the classic fallacy of beginning meditators, who believe the secret lies in choosing what to think, or in fact choosing not to think at all. It makes rational sense as a way to approach suffering; "Thinking this way is causing me to suffer. I must change my thinking so that the suffering stops."
In fact, the fundamental tenet of mindfulness is that this is impossible. Not even the most enlightened guru on this planet can not think of an elephant. You cannot choose what to think, cannot choose what to feel, cannot choose not to suffer.
Actually, that is not completely true. You can, through training over a period of time, teach yourself to feel nothing at all. We have a special word to describe these people: depressed.
The "trick" to both Buddhist mindfulness and MBCT, and the cure for depression if such a thing exists, lies in accepting that we are as powerless over our thoughts and emotions as we are over our circumstances. My mind, the "master" DFW talks about, is part of the water. If I am angry that an SUV cut me off, I must experience anger. If I'm disgusted by the fat woman in front of me in the supermarket, I must experience disgust. When I am joyful, I must experience joy, and when I suffer, I must experience suffering. There is no other option but death or madness— the quiet madness that pervades most peoples' lives as they suffer day in and day out in their frantic quest to avoid suffering.
Experience. Awareness. Acceptance. Never thought— you can't be mindful by thinking about mindfulness, it's an oxymoron. You have to just feel it.
There's something indescribably heartbreaking in hearing him come so close to finding the cure, to miss it only by a hair, knowing what happens next.
[Full disclosure: My mother is a psychiatrist who dabbles in MBCT. It cured her depression, and mine.]