Another main thing I took from him was the importance of not compromising on your principles: when faced with two tough decisions where there is no "right" decision, if you stick to your principles even if it may be uncomfortable, you will feel more certain about the decision you made. But if you decide on something else, possibly for convenience, then that is when you get doubts if you really made the better decision.
RIP Stephen. I was fortunate my mom got me your book to read years ago as a teen, and I knew that I wouldn't need to read other "similar" books. I have never read a self-help book and don't consider yours in that category.