Bailey's speech went viral and he received well-wishes from around the world. More than 1.7 million people have viewed the video on YouTube.
But 18 months later - and now in remission - he told tonight's Sunday programme on TVNZ he almost didn't make it to the assembly.
After a week in hospital receiving chemotherapy, the day he gave his speech was his lowest point.
He remembers getting out of bed and shaving before the prizegiving - the physical exhaustion from that simple act made him vomit.
Bailey had lost nearly 15kg, which was excruciatingly obvious when he tried on his uniform.
"My blazer was like a cape, my arms stuck out at funny angles, my legs were like sticks holding me up," he told Sunday.
He had written the speech before getting sick and was determined to read it.
But an hour before the prizegiving a nurse asked him if he was ready and he said he couldn't do it.
"She said, 'That's fine but I just don't want you to regret it.' I stood up and gave the nurse a hug and my mum wheeled me out of the hospital."
The many lessons the 19-year-old has learnt are covered in his new book, What Cancer Taught Me, released later this month.
A documentary about his life, The Common Touch, will also screen at the Documentary Edge Festival in Wellington on May 11 and in Auckland on June 3.
The hardest part of the battle was rebuilding himself after beating the illness, Bailey told Sunday.
"There's a taboo around cancer and the taboo is transferred onto cancer patients," he said. "It makes their treatment all the more difficult because people almost seem like they're afraid of you."
But he was determined not to let the stigma or the illness break him.
"In adversity you have a choice and that choice is to let it cripple you or grow from that."