"You go to a hospital, they fix the injury. But they don't equip you with the skills to get through the next bit - the recovery," he said.
Grant admitted the side effects of his medication were "worse than the injury itself" and candidly revealed he lived with terrible nightmares where he faced his "deepest, darkest fears" every night and even caused him to sleep walk.
The side effects took a toll on wife of nine years Cheryl - better known as Chezzi - as she was forced to bear the brunt of his erratic behaviour.
Things came to a head when the Gold Logie winner went missing and was found asleep in the fire escape of a building in Sydney's CBD.
"I'm lucky she's still here because I put her through the wringer.
"I've said this before - I said a lot of horrible stuff that I feel bad about," he said.
Grant credits his "beautiful" wife and a new hosting job on Family Feud for bringing him back to his best.
"I was in a bit of a hole. I was a bit lost and Family Feud came along...[it] gave me a ladder out of that hole and I am very lucky to have had it. It gave me my mojo back."
The frank admission comes one month after the celebrity couple told fans their daughter Sailor had a bad allergic reaction.
"Her little throat started to close up. She had hives," Chezzi wrote on Instagram.
"We had to act fast. It’s not the first time, but it was worse this time. I wasn’t expecting it. We think it was cross-contamination of some pistachio nuts on some tongs at a hotel we stayed at."