First on a positive note, the example about attention on sex and arousal feeding back on itself and deepening the experience is well described and easy to relate to. But I think the "deepening an experience through attention" phenomenon applies in so many other domains as well - Sustained attention on a film or video game world, deep uninterrupted creative work for many hours, etc. It's a wonderful positive feedback loop.
It is somewhat similar to how when sitting in silence outside for a long period of time you begin to become aware of more and more subtle details of the experience that weren't immediately accessible. Almost like you're turning up the sensitivity knob on things.
Unfortunately as the author describes, the attention feedback loop can become unpleasant and even torturous when it is directed on negative sensations. For me it has been various things at different stages of my life - muscle tension, breathing, eye floaters in my vision, etc. The same process plays out - Sustained fixation of attention on the sensation increases your sensitivity to it, meaning you notice it more and it bothers you more, meaning you pay more attention to it, and it gets out of control.
The difficulty I experience is that this attention is unwanted and yet I feel my mind focus on it almost automatically. Paradoxically, most of the treatment/recovery advice for this type of OCD is to allow these sensations to be there without rejecting them, which I'm still working on.
But it is helpful to see the positive flip side of the coin too - Our minds are capable of deep focus and deep attention, which can increase sensitivity and let you see increasingly subtle details of experience, making you a better appreciator of art and life, a better creator, a better listener and friend, etc.