Walker said he "got tired" of being someone he wasn't and realised something had to change.
"It all just got me to a place of, what the hell am I doing? This is not me. I got here because I'm me, not because of what they want."
He said when he came back to New Zealand to be a judge on The X Factor in 2013, that he realised he needed to do for himself what he was encouraging other young artists to do.
"I had to come back and find myself again, coming home and spending time with my nannies."
Now he's fully embraced who he is, with his new single Bigger/Tua being released in both English and te reo Māori.
Walker said the song was a tribute to his tūrangawaewae, with the music video featuring scenes from his marae.
Walker said the song was written "for such a time as this".
"Considering where the world is at in 2020, for me it's really solidified what my purpose is and who I am and where I'm going."
Walker also spoke about his experience with lockdown, saying it was "one of the most incredible things" to ever happen to him.
"I got to learn about myself, there was a lot of mending of relationships in my life.
"I was forced to be still ... it was the most still I've ever been since I had cancer."
Walker had his stomach removed in 2017 after he was diagnosed with cancer. He had a rare mutation of the CDH1 gene that runs in his family, and they had already lost 25 family members to the disease.
He took several years out from touring and releasing music but this year he has released Bigger/Tua and a memoir is due out on October 8 titled Impossible: My Story, with HarperCollins New Zealand.
Asked how embracing his cultural identity might affect his commercial success, he said "What sells better than the truth?"
"I'm unapologetically Māori. When people ask 'Are you a Kiwi, are you an Aussie?' I'm Māori, I live in both countries but I'm Māori."
The full interview is on Newstalk ZB after 10am today.