Haven't yet, but I got several chapters in before it got put on hold, and I've already used some of the concepts/techniques, which is impressive for a book. This is also part of why I'm reading it slowly: so I can gradually integrate it.

One that has emerged several times:
Never make an "X or not" decision
IIRC, studies reveal that those decisions are statistically regretted. We don't make them well. By contrast, decisions between 3 or more options are usually well-made. Part of it is that even if you choose one of the original two, you have better context for them.

One technique they recommend is to imagine that a genie comes and says, "About those options you're considering... sorry, you can't do either of them. You have to do something else." ... This little hack works pretty well.