If only we knew then what we know now. Who hasn't said that at least once in their adult life?
If Dr. Emmett Brown turned up in his time-travelling DeLorean and took you for a chat with your high school self, what advice would you give? "Keep taking math, you're going to need it." Or perhaps, "Don't worry, it gets better."
It seems to us that the advice you give says something about the person you've become. It is a reflection of the priorities and ideals that you've developed as you've grown. That's why we find it fascinating to pose this question to the world leaders and everyday heroes we meet at We Day, a youth empowerment event now held in eight Canadian cities, and as of last week, Seattle.
Media legend Larry King, Olympian Sylvie Fréchette, Aboriginal leader Shawn Atleo, Canadian hero Roméo Dallaire, heiress and social entrepreneur Holly Branson, and peacemaker Desmond Tutu all reflected on what they would say if the DeLorean showed up at their doors.
Larry King, the award-winning American TV and radio news host, would tell himself that if you want something, pursue it and don't let setbacks get you down.
"Never give up when things look the bleakest. There will always be a tomorrow and when I look back, the biggest worries I had weren't that test on Monday, that girl who didn't return my phone call, that sad day my team lost."
Canadian synchronized swimmer Sylvie Fréchette has brought home Olympic silver and gold. She's no stranger to success. But if Fréchette had a few minutes alone with teenage Sylvie she'd advise,"Don't be afraid to fail."
Throughout high school Fréchette felt pressure "to make the right choice" and avoid failure. "I wish someone had told me this when I was in high school. If you fail it's because you tried something. You went out of your comfort zone, and you're going to go to bed tonight knowing more about yourself."
Shawn Atleo, the Assembly of First Nations national chief, says that when he stands in front of an audience of young Canadians, he feels like he is talking to his younger self. The advice he shares now is the advice his father gave him when he was in Grade 11.
Young Atleo was stumped by an algebra assignment. Throwing his hands up in frustration, Atleo told his father he just couldn't get it.
"You can have what you say, son," his father calmly replied.
His father's message, and Atleo's message to young people today, is that if you say you can't do something, you'll talk yourself into not being able to. Achieving means believing that you can.
"I had to repeat Grade 11 algebra in Grade 12 and I got through it the second time around by just learning that I have to get out of my own way and do the hard work," Atleo recalls.
Although they come from vastly different worlds, Roméo Dallaire and Holly Branson have remarkably similar advice.
Dallaire is a Canadian Senator and retired General who led UN efforts to stop the Rwanda genocide and now leads a global crusade to stop the recruitment of child soldiers. Dallaire would urge a young Roméo to "get off my butt" and start an NGO, either locally to address issues like Aboriginal poverty, or working in developing countries. He urges young people to get out and travel in Africa, Asia or South America -- but not Europe.
"The churches in Europe will still be there when you're old. When you're young, get into the field and get your hands dirty."
Holly Branson, daughter of the British travel and media mogul Sir Richard Branson and heiress to the Virgin business empire, would also press her high school self to get out into the world.
"Get out there and do as much as you can now to change the world while you're in school. Because when you leave all of those opportunities won't be there."
Perhaps the most concise and poetic counsel comes from our own hero 'The Arch' -- Archbishop Desmond Tutu. What would he say to his younger self?
"Go on dreaming."
When you have a moment today, write down the advice you would give your high school self. Even though you have no time machine and will never be able to deliver it, that advice is not wasted. Those lines contain a reflection of the person you wanted your younger self to become -- the person you want to be now.
Craig and Marc Kielburger are founders of international charity and educational partner, Free The Children. Its youth empowerment event, We Day, is in eight cities across Canada this year, inspiring more than 100,000 attendees. For more information, visit www.weday.com
Photos From We Day 2012 Toronto
Follow Craig and Marc Kielburger on Twitter: www.twitter.com/craigkielburger