"Alcohol changed my life, alcohol gave me confidence," he said. "My biggest fear was that people were going to take the piss out of me."
He said alcohol stopped any hurt directed at him and "shut the noise up" in his head.
"From that day forward whenever I needed confidence, I drank. Whenever I was hurting, I drank. Whenever I needed sleep, I drank.
"I used to do just enough to get me through the day ... but I still had the demon."
Mr King, who has been sober since 2007, said: "The beautiful thing about giving up drugs and alcohol was developing a sense of right and wrong."
He also spoke of how he started the Nutters Club on Radio Live in 2009, a programme publicising depression and offering people a chance to express their thoughts and recover from or manage the illness.
"I guess my message to you fellas is you are just wasting your time trying to be macho, and trying to put on a tough face.
"Forget about all that stuff. It's not worth it."
Principal Corrections Officer Lawrence Ereatara said Mr King was someone the prisoners could relate to.
Mr King held a parenting talk at the Havelock North Community Centre last night which addressed how parents could stay connected with their kids.
He will hold another parenting event tonight at the Napier War Memorial Centre at 7pm, by gold coin donation.