What advice would you give your twenty-year-old self, and what should they ignore?

When I recall my own path of life I cannot but speak of the violence, hatred and lies. A lesson drawn from such experiences, however, was that we can effectively oppose violence only if we ourselves do not resort to it.

History was not written by men who predicted failure, who gave up their dreams, who abandoned their principles, who allowed their laziness to put their intelligence to sleep. If certain men at times were alone in seeking victory, they always had at their side the watchful spirit of their peoples, the faith and destiny of many generations.

When I went through school, I was in a hurry. I was an economics major as an undergraduate, and I was a finance major in graduate school. I was in a hurry to succeed when I got out in the business world. I’m sorry I didn’t take more courses in the humanities and in history and in the arts.

I go back to this idea that I only discovered when I was older. I wish I had known it when I was younger, because I think I missed a lot of observations in life. That is to develop your own philosophy. I always thought philosophy was one of the most useless subjects in the world.

I’d tell them, “If you believe in something, go for it, but know that when you go for it there’s a price to be paid. Be ready to pay that price and you can contribute to the welfare of society, and society will acknowledge you and respect you for it. And don’t be afraid. Don’t be afraid.”

If you want to do something, one of the smartest things that you can do is go find someone that’s done it and to try to get them to show you how they did it, to show you where the potholes are. What are the right steps to get there? ... And not just in terms of where to go to school, but what are the things that are really tough that you have to overcome, and how did you overcome it.

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.

My grandfather looked at me, and after a bit of silence, he gently and calmly said, “Jeff, one day you'll understand that it's harder to be kind than clever.”

And the most fulfilled, centered, grounded, happy people I know are people who made the choice to be part of an effort to actually make the world a better place. ... I would say, to me, the path of least regrets is to at least make a short-term commitment to say, “Let me work to make a real difference in the world.” The worst that could happen is you decide to move into something else later, but you’ll always take with you what you’ve given and what you’ve gained through that experience.

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.

Learn by doing, not learn first, then do. The way you discover what it is you like to do in life is by doing first, then learning about it.

My key message to her, as a nine-year-old, recently has been, “You don’t need to be friends with everyone, but you’re forced to respect everyone. And everyone doesn’t need to be friends with you, but everyone is forced to respect you.”