Speaking at a charity event here, Harry said, "The decision that I have made for my wife (Meghan Markle) and I to step back is not one I made lightly."
"It was so many months of talks after so many years of challenges and I know I haven't always got it right, but as far as this goes there really was no other option."
However, the Duke of Sussex made clear that he and Meghan were "not walking away".
"The UK is my home and a place that I love, that will never change," he said.
It is the first time Harry has spoken publicly since it was announced the couple would give up their His and Her Royal Highness (HRH) titles and will also no longer formally represent the Queen.
During his speech, he said, "I can only imagine what you may have heard and perhaps read over the past few weeks.
"So I want you to hear the truth from me as much as I can share, not as a prince or a duke but as Harry."
The Duke of Sussex said he would always have "the utmost respect for my grandmother, my commander in chief".
"Our hope was to continue serving the Queen, the Commonwealth, and my military associations, but without public funding. Unfortunately, that wasn't possible," he said.
"I've accepted this, knowing that it doesn't change who I am or how committed I am."
As part of a deal finalised on Saturday between the Queen, senior royals, and the couple, from the spring this year, they will stop using their HRH titles and withdraw from royal duties, including official military appointments.
However, the statement by Buckingham Palace said they would continue to maintain their private patronages and associations.
( With inputs from IANS )