Sailor was suspended from all professional sport after testing positive for cocaine in 2006 and said such moments were turning points.
"I learned a hard lesson about respecting the game and people. And people will respect you more if you put up your hand: 'I did the wrong thing'."
Former All Black Norm Hewitt said he hoped the NZRU wouldn't give up on Guildford.
Hewitt, a former All Black hooker, drunkenly broke into the wrong Queenstown hotel room in 1999.
His actions at the time made national news, and at a press conference organised by the NZRU to apologise for his actions, Hewitt broke down in tears.
It proved to be a life-changing moment, for it was then that Hewitt finally realised how serious his drinking problem had become.
"Do we persevere with this young man? Absolutely," he told Radio Live. "Absolutely, I've got all the confidence that Zac can get through this and work through this and become better - not just as a rugby player but as a human being."
Alcohol Healthwatch director Rebecca Williams said Guildford had several options to tackle his drinking.
"Those young sports players are under a lot of pressure to perform and be role models.
"At the same time they're exposed to the incredibly aggressive alcohol promotion - the teams are sponsored by alcohol, there's alcohol all around them with the promotion of it."
Guildford has appeared before the New Zealand Rugby Union three times in the past 18 months.
Alcohol Advisory Council of New Zealand chief executive Gerard Vaughn said programmes which might help Guildford included Alcoholics Anonymous and community alcohol counselling initiatives.
He agreed with Ms Williams in saying complete abstinence from alcohol may not be necessary.
Ms Williams said the dangers for Guildford go further than physical harm while intoxicated because at 22 his brain is still developing.