[mrvir]

I wish that, in my twenties, (1) I knew this, and (2) I had the balls to be brutally honest with myself about what my strengths and weaknesses were

I actually agree with the advice on working on your weaknesses early in life, because pushing your limits helps you better understand yourself. I don't think I was dishonest about myself earlier, maybe too idealistic trying to fix some weaknesses that I nowadays consider part of my personality. And I'm not talking about skills here, but more about mental debugging of your emotions, ambitions, relationships etc.