I posit that it's something that will make you think it worked (and you'll recommend the book to all your friends), but won't make any actual positive impact on your discipline. Basically if it's a placebo, it would give you self-delusion instead of results.
Actually, the placebo effect is not a delusion, that's why it's called that and not "the placebo delusion." A better analogy would be something that worked despite not believing that it will. Results despite opinion, as it were.
The upshot is that discipline is self-evident. Anything that has an effect on discipline is indistinguishable from placebo. Either you're getting more done or you aren't, there's not a lot of room for "getting stuff done, but in a fake way."
Unless you take time to measure how much you get done (how would you even measure such a thing consistently?) - you might think you're getting more done even though you're not. Kind of like multitasking can feel really productive, even though productivity actually decreases.
I posit that it's something that will make you think it worked (and you'll recommend the book to all your friends), but won't make any actual positive impact on your discipline. Basically if it's a placebo, it would give you self-delusion instead of results.