His habits. You can’t regularly work 80 hour weeks without packing a few tricks. You can’t build multiple billion dollar companies without knowing something others don’t. Often I find when talking to successful people, they’ll make a revealing offhand comment that’s pure gold and can in fact change your life - if you’re paying attention.
An example might be Einstein and Steve Jobs having a full wardrobe of duplicates of the same outfit. Ok, but why? Because they realize the mind is only capable of resolving a finite number of dilemmas per day and choosing what to wear depletes that resource. An eccentric habit, but revealing indeed. After being sold on the theory, they went all in. I wonder to what degree they executed on insights like that where the rest of us just brushed them off