Go with my gut more often, stop taking other people's advice against my gut feeling.
I'm in a pretty good position based on my own merits.
But I moved in with a friend at the advice that I'm too young to be living alone. I'm starting to miss it.
I would have earned a lot more and be much further in my career, potentially already employing people, if I hadn't listened to my peers and mentors when it comes to career advice. I should have looked at their position, given their age and compared it with my own. Technically they're amazing, career and money-wise, they should be much, much further ahead than I.
Save more. Get better with finance administration. Set hard goals and break them. Just because you earn almost 10-fold your first job, doesn't mean you should be spending more than you were before. Money drives business drives ideas drives change.