I've long been interested in writing a book called something like "Manifestation for Rational People"

I think there's a lot of benefit in practice of some woo-woo things.

I love finding things that shouldn't help in theory, but are gamechangers in practice.

One big one is not overthinking things. Smart people are exceptionally good at over-justifying, over-explaining, over-rationalizing. Especially to themselves! If you want to do something and it isn't going to harm someone else, you don't need to over-justify it to yourself or others, you can just do it.

Another would be certain therapy systems like Internal Family Systems that involve treating yourself as a set of parts. Imagine visualizing the different voices in your head or your subconscious like they're your own children, and then help them like a great parent would help a toddler.