Speaking in an ITV documentary about his charity work in Lesotho, the prince said losing his mother at a young age made him question his position.
He said he used to "bury his head in the sand" but now views life "very, very differently".
Harry co-founded the Sentebale charity with Prince Seeiso of Lesotho to help young people affected by HIV/Aids.
The 32-year-old prince told the programme: "I always feel like I need to make something of my life.
"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."
Sentebale has delivered adolescent HIV testing and counselling services to more than 21,000 people since it was founded in 2006, and plans to expand into several sub-Saharan African countries by 2020.
Harry was interviewed by broadcaster Tom Bradby, who shadowed the prince when he first visited Lesotho 12 years ago.
The prince said it was "fun to be good and boring to be bad".
"If you're me, if you're your Average Joe, 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 programme, due to be broadcast on Monday 19 December, also features contributions from musicians Sir Elton John, Joss Stone and Chris Martin of Coldplay.
Harry is reunited with a teenager he met on his first visit and is seen dancing with local children.

The four national football associations were unable to agree on sending Great Britain teams to Rio.
Sampson, who led England to a bronze medal at the 2015 World Cup, described the situation as "frustrating".
"I've watched the tournament and I believe this team would have won the gold medal," he said.
"This group of players did earn the right to go to an Olympics and represent themselves and their country, but it's been taken away from them".
England captain Steph Houghton, who scored three goals at London 2012 for Great Britain, added that it was "very disappointing" to not go to Rio.
"That was originally our place - the place that we won at the World Cup, and it's hard, but at the same time there's no point about complaining we can't be there," she added.
England's Football Association had put forward the idea of sending Great Britain teams to the Olympics, but Fifa said it would need the agreement of the ruling bodies in Scotland, Wales and Northern Ireland, who were against it.
Stewart Regan, the Scottish Football Association's chief executive, has been among those to voice concerns that a Great Britain team would threaten the separate status of the home nations at future international tournaments such as World Cups.

The work, entitled Duality, is formed of diptychs, with each person posed in their own clothing and their workwear. The aim is to see how a viewer responds to the uniform and how it shapes their perception of that person - how we prejudge based on a uniform or a certain look and style.
Of course, what we wear also affects us, our approach and how we feel.
What is your response to these pictures?
The images are on show at the No Walls Gallery as part of the Brighton Photo Fringe Festival. I'll be highlighting some other work on show at the festival next week.
All photographs courtesy Strand Collective.
Prince Harry has said he no longer struggles with his royal role and wants to "make something" of his life.
[NEXT_CONCEPT]
Great Britain could have won another Olympic gold had the women's football team been allowed to compete, believes England head coach Mark Sampson.
[NEXT_CONCEPT]
New work by Simon Bray and Tristan Poyser explores the way in which our clothes shape us, that outer shell we use to accentuate or sometimes hide who we are.