Life doesn't offer you the perfect opportunity at the perfect time. Opportunities come when you least expect them ... Rarely are opportunities presented to you in a perfect way. In a nice little box with a yellow bow on top. ‘Here, open it, it's perfect. You'll love it.’ Opportunities -- the good ones -- are messy, confusing and hard to recognize. They're risky. They challenge you.

No. Go for it, as I did it. Go for all the mistakes. I made so many mistakes in doing my films. They all have a stutter or a limp or they are squint-eyed. Hardly anyone notices it, but I notice. Make your mistakes. Get arrested if you trespass. Yes. Do it. There’s nothing wrong with spending a night or two in jail. I’ve done that. Don’t be afraid of the grizzly bear behind you. Travel on foot. Read books.

Sensitivity. Be sensitive in every way possible about everything in life. Be sensitive. Insensitivity brings indifference and nothing is worse than indifference. Indifference makes that person dead before the person dies.

So given a Time Turner, I would tell my 21-year-old self that personal happiness lies in knowing that life is not a check-list of acquisition or achievement. Your qualifications, your CV, are not your life, though you will meet many people of my age and older who confuse the two. Life is difficult, and complicated, and beyond anyone’s total control, and the humility to know that will enable you to survive its vicissitudes.

Microsoft was at the center of the personal computer revolution, and particularly the creation of a software market where you went out to lots of companies, and encouraged them to write software for different applications, mundane applications, wild applications. That idea that you would encourage people to be creative, and build software, and there would be a whole industry around that.

I read Stephen Pinker's The Better Angels of Our Nature a few years ago and got to talk to him about it after, which was a lot of fun. I reviewed it for my blog, Gates Notes, because I wanted other people to read it, love it, and hopefully learn from it the way I did. It's probably my favorite book and the one I recommend most often.