Harry, who stepped down as a senior working royal in March, said the decade he spent in the Army changed him for the better.
Speaking to the Stand Up For Heroes event in the US, he outlined the importance he placed on his 10 years in the military, which included two frontline tours to Afghanistan.
The duke, who was left saddened when he was denied his wish for a wreath to be left on his behalf at the Cenotaph on Remembrance Sunday, said: “(My military) experience changed my life forever and for the better.
“It changed how I viewed sacrifice and service. I was born into a life of duty, but it was during my decade in the army that I committed to a life of service.”
He said he would always be part of the military team, and paid tribute to those he met while serving.
“My experience in the military made me who I am today – and it also connected me with some of the strongest, funniest and most memorable people I’ve ever met,” he said.
“Once we join this team, we are always part of this team. Once we’ve served, we are always serving, and proudly so.”
Harry and his wife Meghan, the Duchess of Sussex, quit royal duties nearly nine months ago to pursue a life of personal and financial freedom in the US.
This meant his honorary military titles – Captain General of the Royal Marines, Honorary Air Force Commandant of the Royal Air Force Base Honington, and Honorary Commodore-in-Chief of the Royal Naval Commands’ Small Ships and Diving – were put on hold.
Harry is not allowed to take any particular role using those titles at present, but they have not yet been handed to other members of the royal family.
His role will be examined in March as part of the monarchy’s 12-month review of the Sussexes’ departure arrangements.
The Stand Up For Heroes comedy event helps raise money for military veterans in the US.
Hosted by Jon Stewart, the annual fundraiser is presented by the Bob Woodruff Foundation and the New York Comedy Festival, and celebrities taking part include Bruce Springsteen, Sheryl Crow and actor Ray Romano.
Harry, who set up the Invictus Games competition for injured servicemen and women in 2014, added: “I wanted to honour the legacy of these men and women who have given up so much – from time with family to birthdays missed and even births missed.
“Some lost their limbs and others lost their lives. It’s for that reason that I created the Invictus Games – to give injured servicemen and women a platform to excel and reaffirm their values of resilience, of community and strength, which are inherent in each and every one of us.”
He also spoke of the challenges people have faced during the global pandemic.
“For the whole world, this year has been and continues to be incredibly hard,” he said.
“But we’ve also seen incredible resilience and purpose. As far as I see it, service is what happens in the quiet and in the chaos. It’s what happens when people aren’t looking and it’s about how we take care of each other every single day.”
The Sussexes paid a private visit to Los Angeles National Cemetery on Remembrance Sunday, but were accused of staging a publicity stunt after they were photographed there by Lee Morgan, who specialises in fashion and celebrity portraits.
Those close to Harry said he was not the sort of person to make a stunt out of a Remembrance event, particularly having known fellow service personnel who died.
Last week, he volunteered by helping to pack and distribute food parcels to military veterans and their families.