It is unfortunate that this method has been applied to things with no substance at all, like The Secret. However, it certainly would not on any level be deceptive or promise anything it couldn't deliver.

People want to win. That's what LW rationality is for. That is, in point of fact, what we promise. You seem to be objecting to saying so upfront.

Is it worth introducing simple rationality tools to people who would otherwise think The Secret was a good idea? Or is that something you think should be avoided in general?

Using it as the only hook possibly wouldn't be good and might lead to the effect you describe. However, brainstorming is cheap. What I'm saying is "ideas, ideas, please come up with lots."