The 32-year-old, speaking in an ITV documentary about his charity work in Lesotho, said he used to “bury his head in the sand” but now views life “very, very differently”.
“I always feel like I need to make something of my life,” he said.
“I was fighting the system going ‘I don’t want to be this person - my mother died when I was very, very young and I don’t want to be in this position’.
“But now I’m just so fired up and energised to be lucky enough to be in a position to make a difference.”
Harry co-founded the charity Sentebale - meaning “forget me not” - with Prince Seeiso of Lesotho in 2006 to improve prospects for the thousands of children and young people affected by HIV/Aids in the landlocked African country.
It has since delivered adolescent-friendly HIV testing and counselling services to more than 21,000 people, and plans to expand into four or five sub-Saharan African countries by 2020.
Harry first visited Lesotho 12 years ago, shadowed by broadcaster Tom Bradby, who interviewed the Prince for the documentary.
In the film, Harry urges people to do good, claiming it is “fun to be good” but “boring to be bad”.
“If you’re me, if you’re your Average Joe, if whoever you are, if you can’t affect politics and change the big things in the world then just do whatever you can do - whether it’s in your local community, your village, your local church - walking down the street, opening a door for an old lady, helping them cross the road. Whatever if it is, just do good. Why wouldn’t you?
“The good stories are what make people tick everyday, surely? It’s fun to be good and it’s boring to be bad, but you can be naughty as well.”
Harry also receives praise in the documentary from Sir Elton John, who urged people to go to see the work being done by Sentebale, saying: “If his mother was alive, she’d still be doing the work she set out to be doing, and he’s carrying it on in the best possible way.”
The film, which also features singer Joss Stone and Coldplay frontman Chris Martin, shows Harry being reunited with a local teenager, Mutsu, whom he met on his first visit to Lesotho, and the Prince dancing with local children.
:: Prince Harry In Africa will be broadcast on ITV at 9pm on Monday.