His instinct was to "run away". He almost ran off the field during one game, and missed another game altogether.
Over five or six years from the age of 20, he learnt gradually to identify the fear as just a feeling that couldn't harm him - to "cuddle the fear".
"The last thing that ugly creature wants is a cuddle," he writes. "So grab hold of it and give it a cuddle - this breaks it down a wee bit and takes the fear out of it. If you can address and understand your fears, communicate them to the people who matter, and then 'cuddle' those fears, you take away some of their power."
Kirwan's children have spent most of their lives in Italy, where Kirwan started playing rugby in the off-season in 1985 while he was still an All Black. He later coached the Italian rugby team from 2002-05, and commuted from Italy to Japan to coach the Japanese team from 2007 until the 2011 Rugby World Cup.
Sir John and his son Luca. Photo / Supplied
He married his wife Fiorella in 1991 and the family lived in a 200-year-old villa in rural Treviso, close to her parents who are still there for Francesca.
Kirwan wrote about a Skype call from Francesca in the book extract on this page to "show some vulnerability as a parent", to say "it's OK to be worried".
"If it's just a homesickness and missing Mum and Dad but life's good, then as long as you're there saying the right things, in that case the wrong thing would be to say give up and fly home," he says.
"But if it lasted a bit longer, the right thing to do might be to get on a plane and go up there or get her to come down. So it's just about the identification and what you do. I mean, there's no rules, are there?"
His sons have had to adjust to life in New Zealand since their dad took the Blues coaching job two years ago.
"Changing countries and stuff is not easy on the kids," he admits. "I tried to stand next to them and understand the emotions so that they had somewhere to go, and it was OK to not like it or discuss it."
If he had never experienced depression, Kirwan believes, he would have been "a lot more self-centred and not as well balanced". He believes our society generally is too self-centred and too busy. "We are going the American way, so very busy," he says.
Sir John's daughter, Francesca, is a professional volleyballer in Italy. He says changing countries "was not easy on the kids". Photo / Dean Purcell
"I just think we need to get back to the fundamentals, which are family-based, so for me I think we need to be very careful to go this whole capitalism, commercialism drive to get the material things in life. I just think we all need to take a breath and say, 'OK, if that's the life I want, that's fine, but there are consequences.'"
In Italy, school starts at 8am and finishes at 1.30pm, and workers have a two-hour siesta from 1.30 to 3.30pm so the family has lunch together. Although that is not possible here, the Kirwan family still eats the evening meal together - with no cellphones during dinner. Kirwan writes that their most important emotional glue is shared vulnerability.
"Because I'm vulnerable with my kids, they can be vulnerable back at me," he writes. "They're as involved in the Blues as I am, mentally," he says. "So discussing, 'I'm pretty upset we lost', or 'I'm pretty stressed about the team not performing as it should,' so taking them on the ride, so we share some of the load, so they're aware of it, and then I try to get time with them as much as I can."
Often teenagers don't want to talk. But Kirwan has learnt from researching the book to give his teens full attention when they do talk.
"I've been sitting around and he [his son] has come up and wanted to chat, so I'll just sort of drop doing all this and listen. You know, sometimes you've got to listen to another language, so you've got to listen to what they're saying to you, you've got to be there while they open up."
When he is at work or away, he is available by mobile. "It doesn't matter how you communicate as long as they know that when they need to communicate, you're there."
He has learnt not to minimise things.
Sir John in his All Black days. Photo / New Zealand Herald
"I talk in the book about as you get older you see the whole house, but when you're a teenager you just see the room," he says. "For me it's about understanding the room, just digging a little bit deeper and trying to understand it a wee bit more, not 'You'll get over it.' Because right at that moment it's probably the biggest thing in their lives."
Kirwan writes in the book that mental wellness comes from slowing down and taking time to be kind to others. In his own life, talking about his depression on TV advertisements and on the depression website has encouraged thousands of people to come up to him, in supermarkets, at airports or in the street, to tell him their own stories.
As his son Luca said to him when he witnessed one of these moments during filming for the book's cover photo at a beach: "Gee, that must feel very special, Dad, when that happens."
It explains how Kirwan could tell Sarah Daniell in 2012 that depression was "the best thing that ever happened to me".
"I don't wish it on anyone, it was my worst nightmare," he says. "But through it I am a better, stronger, more compassionate person."
Sir John Kirwan will speak about his book at Hamilton Boys' High School on Thursday October 9, 7.30pm, and at Kristin School, Albany, Friday October 10, 7.30pm. For more information CLICK HERE, or for tickets CLICK HERE
WHERE TO GET HELP
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (4pm to 6pm weekdays)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• The Word
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• CASPER Suicide Prevention
If it is an emergency and you feel like you or someone else is at risk, call 111.
