Adrenaline is an addiction no sportsman wants to kick.
For many, ending the search for the buzz is one of life's hardest calls.
Performing at your peak at the highest level creates a rush that leaves you craving more.
Success drives hunger for that sensation; fuels the motivation to seek out those euphoric emotions few get to experience.
"It's more addictive than any drug," Western Australian boxer Danny Green told Sunday News of his triumphs in the ring.
"From that first training session in our family front yard I was hooked.
"It is a very alluring relationship to have; because of the highs it's very addictive. I don't think any drug could beat the feeling of being victorious in front of a huge stadium, having trained so hard with your team and formed that bond and given up everything."
So what happens when the time comes to let go; to give up the irreplaceable source of self- accomplishment?
Unlike heroin, cocaine, ecstasy and other illicit substances, there are no rehabilitation clinics for cutting ties with your love; your passion. And, at the elite level, there is no way of being weaned off this form of addiction.
"In that one moment when the referee raises your hand and the crowd are jumping up and down and the lifetime of dedication pays off, it's an awesome feeling, but I understand it can't last forever," says Green, who will be striving to replicate that exact moment against Shane Cameron in Melbourne this month.
After their battle for the IBO world cruiserweight title, Green expects to walk away from the sport - this time for good.
He tried once before to kick the adrenaline habit.
In late 2007, seven years after turning pro to get a house deposit, and 17 years after his first amateur fight, Green claimed the WBA light- heavyweight title at home, in Perth. Three months later, the surfie from the beach-side suburb of Scarborough made the shock call to quit. He was finished.
It was over - or so Green thought.
"I woke up one morning and said 'that's it. I'm done. I'm retired'. I had a strange gut feeling telling me to walk away," he recalls.
But the void was too great. Green needed his fix. He couldn't shake the desire, and dependence.
"After about eight months I had a scratch that needed to be itched. I was really worried about coming back because I said I wouldn't," he says.
That would be the turning point.
One year after retiring, Green returned. He jumped to cruiserweight, where he would become a three-time world champion and record a stunning TKO first- round victory over Roy Jones jnr, the renowned American who secured six titles in four different weight classes.
"It's been the most lucrative period and the biggest highlight of my career."
Those boxing achievements evoke joy and feed the addiction, but losses emphasise how lonely, and emotionally draining, the sport can be.
Green almost threw in the towel again last year.
Successive defeats to American Antonio Tarver - later stripped of his title for steroid use - and Polish champion Krzysztof Wlodarczyk rocked his spirit. He was broken.
The Wlodarczyk bout was a devastating defeat. After being ahead on all scorecards, Green was clocked in the 11th round. Many suggested he should leave the craft.
The qualified carpenter and father of two - Chloe, 11, and Archie, 5 - agonised about hanging up the gloves. The all-consuming disappointment sent him to dark places.
This long-awaited scrap with Cameron, which has been two years in the making, almost never happened.
"I sucked a few cans . . . went a bit loose for a while," Green says of his self-reflection. "I had a bit of a blowout. I wasn't sure what I was going to do. I was very disappointed because I came so close [against Wlodarczyk] after working so hard."
It hasn't been easy, but the 39-year-old has come to terms with the reality he can't keep fighting. His hands are mangled - a handshake is a difficult task. His body can't take much more. There's only so much punishment one man can endure.
But after 21 years of involvement, life after boxing remains a scary prospect.
The desire to beat Cameron and leave a lasting legacy - as the first Australian to win four world titles - pushes him for one final fight.
"I want to leave the sport with people wanting to see me fight more," he says, wholeheartedly.
"I can try and cling onto the dream as long as I want, or I can be realistic. I've had a good career. Everything has to stop at some point.
"I'll be honest; giving this up is going to be very hard. Sometimes you've got to make a decision that, in the long run, is going to be better.
"If I hadn't of got here it might have been a less difficult decision to make.
"But having been successful, and far exceeding my expectations, it will be bloody hard."
After 37 pro fights - 32 wins and 5 losses - Green has learnt to sense his opponent's tenacity and resolve.
Cameron's is undeniable. Green has seen it, smelt it and will soon confront it head-on.
"His performance against [Monte] Barrett made it very exciting for a fighter. He looked good, he fought well, he put him away with an incredible knockout," Green observes.
"I've been around long enough to smell confidence; smell anticipation and the possibility of achieving something really big for him and this country. You can see it in the way he walks around."
Green appears more at peace with the imminent end.
On November 15, we will find out whether he gets to write the closing chapter on his drug of choice.
- © Fairfax NZ News