"I had partied all weekend, there was no thought of self-preservation when I played, and it kind of went into how I lived my life outside the field as well," Williams told television presenter Lisa Wilkinson in an interview on Australian Channel 10's The Project.
"I woke up to the doctors standing there, a couple of doctors standing there, my girlfriend at the time crying and just remember copping it from the doctor.
"I didn't know any better."
Williams confessed to still feeling guilty about how he treated women and his own body, abusing himself with drugs and alcohol.
"I'm not proud of it by any means, but I'm proud of the man I am today because I've learnt from those experiences," he explained.
"For so long I got manufactured highs from drugs, abuse, womanising, and then the next day I would wake up and I would have such a disgusting feeling in myself and feel like, man, so empty, you know, soulless."
Williams also revealed he still suffers from anxiety "every day".
"But now when I do good things, it is a different type of high," he said.
"It's such a great high, when you visit the sick in hospital, when you give your time for the less fortunate or you make a young kid's day, because the wake-up, the next day, it is of empowerment."
As the NRL continues to be plagued by off-field dramas, including drug scandals and allegations of sexual assault, Williams believes it would be beneficial for the league to start "upskilling" youngsters who join the competition.
"I think we need to be more diligent in the sense that a lot of the understanding that a lot of these youngsters come straight from school, straight into professional sports. They don't have a lot of the experiences in life," he said.
"We need to start upskilling them … understand that you are a role model whether you like to admit it or not."
In his autobiography, Williams reveals that he and his wife got married just four weeks after meeting, admitting the couple were not in love when they tied the knot.
