Sir Richard Branson is determined to enjoy his favourite sports into his eighties and says his philosophy in life is to "dream big".
The 62-year-old Virgin tycoon was speaking before the start of the Virgin Active triathlon in London, in which more than 14,000 people will swim, cycle and run around the capital over the course of the weekend.
As he prepared for what is described as the largest event of its kind in the world, the billionaire said that despite what people may think about his wealth and exciting life, his health and fitness meant everything to him.
"You can have everything you possibly want but if you don't have health and fitness you don't have anything," he said. "I'm an enormous believer in setting yourself a challenge every year and trying to accomplish that challenge. I'm lucky my kids are of an age when we can do wonderful challenges together."
Sir Richard, who says he is still fit and healthy, does not dwell on the prospect that he may in the future not be as able to join in with sporting events.
He said: "I don't worry too much, because kite-surfing is my main sport and that's something I think I can do into my eighties, and there's tennis I can still do into my eighties. Running you maybe have to be a bit careful of, but swimming you can do into your eighties. As long as you don't suffer too many injuries then you should be able to carry on doing it for a long time."
Sir Richard's was taking part in the triathlon in a relay team with his children Holly, 29, and Sam, 26, and will be joined by celebrities including David Hasselhoff, Nell McAndrew, Gareth Gates and Alexandra Burke.
The Virgin boss said he was hopeful his children would see and enjoy one of his other passions in life, space travel, which he is determined to make possible for people around the world.
He believes it is "extremely important" to colonise another planet in case of Earth is struck by a giant meteor or a disease getting out of control.
"We've got a long way to go but by setting seemingly impossible tasks in my life I hope to inspire all our engineers and technicians at Virgin Galactic to not just reach for the skies but to reach way beyond them," he said. "I hope it will happen in my lifetime, it will definitely happen in my children's lifetime," he said.