It's a massive lesson because as much as I thought I can do all the work for him, I can make him better, I can take it away, I can help ... at some point you just have to say, 'I love you and I'm here when you decide to do the work. And if you don't, then that's it'.
"You cannot save a human being, they have to save themselves. But you can love them and give them enormous support and love."
Urban spoke about his battle with drug and alcohol addiction in Rolling Stone earlier this year and said, "The whole back end of the '90s were just awful."
The country music star recalled a binge in 1998 that he thought at the time would end his life.
"I had plenty of stuff," he said to Rolling Stone.
"I didn't seem able to stop. There was no stopping this time. I'd go to sleep, wake up a couple of hours later, go at it again, drinking to take the edge off. I remember thinking, 'I'm probably not going to make it until tomorrow'. And then I thought, 'F**k it. I really don't care. It'll be a relief to not have to. I'll take an Ambien and at some point I'll pass'.
"I was taking everything. I remember thinking, 'Oh, good, this is the end of it, yahoo'. I was quite happy about it.
"Well, I woke up the next day at lunchtime, in my bed, sweating, going, 'F**k! Guess I'm not going to get to go this way'. I thought the choice to quit would be taken from me, which would be easier than me trying to do it on my own. There was coke left, so I went at it again."
Urban, who had two stints in rehab before he married Kidman, credits his wife's 2006 intervention with saving his life.
"I caused the implosion of my fresh marriage," he said to Rolling Stone.
"It survived, but it's a miracle it did. I was spiritually awoken with her. I use the expression 'I was born into her', and that's how I feel. And for the first time in my life, I could shake off the shackles of addiction."