The 24-year-old McFly bassist was treated for depression at The Priory in February 2011, and admitted it was triggered by trying to take his own life when his drinking got out of control.
Speaking during a recording of Alan Carr's Chatty Man, Poynter agreed with Carr when he said the band's autobiography Unsaid Things... Our Story "got really dark".
Poynter said: "It's always good to reflect on that sort of stuff. I'm in a really, really good place now. It is quite easy to forget.
"It's quite therapeutic to go back, quite scary and a bit of an eye opener into how dark it can get if you take your foot off the gas and stop looking after yourself."
The I'm A Celebrity... Get Me Out of Here winner said he was often "so battered" that he didn't know what he was doing.
Commenting on Poynter's suicide attempt, a friend told The Mirror: "We were all devastated.
"His drinking was out of control and he thought ending it all was the easy and perhaps only option available to him."
Poynter and McFly will appear on Alan Carr's Chatty Man this Friday (October 12) at 10pm on Channel 4.