Four-time world champion Carl Froch announced his retirement from boxing on Tuesday after over a year out of the ring and said: "I think the desire has gone."
Super middleweight Froch, nicknamed The Cobra, twice won the WBC title, as well as taking the WBA and IBF belts, during a highly successful career.
The 38-year-old Nottingham fighter won 33 of his 35 fights, with 24 of those coming by knock-out.
He defeated arch-rival George Groves in a Wembley Stadium re-match which turned out to be his final fight in May of last year.
Froch said: "I'm incredibly proud of what I have achieved in boxing but now is the right moment to hang up my gloves.
"I have nothing left to prove and my legacy speaks for itself.
"I've got no regrets. I'm not retiring undefeated but in many ways that's better because I've boxed everybody, I've faced every challenge.
"So many athletes, not just boxers, don't get their defining moment. I've probably had seven or eight defining moments, but the biggest and best was on the platform of Wembley Stadium in front of 80,000 fans. It was amazing and to get that defining moment is enough."
Froch, who will become a boxing pundit, told Sky Sports News: "If I could fight again physically I would, but mentally I'm not sure. I think the desire has gone.
"There will always be options and it's never going to stop. There's always going to be somebody next in line or ready to try to take my scalp.
"And if that's never going to go away, at what point do you say, 'Right, now is the time to retire', based on challengers and opponents?
"You can't wait for that, it's got to be from within here, and as much as it hurts, and as hard as it is for me, and even making the decision to retire and saying it's been a year, it's too long, the fighting machine has gone, it's not going to come back, it's still hard.
"The last thing I think about before my head hits the pillow is boxing, and when I wake up in the morning to think what time it is, and I think it's half six, seven o'clock, should I be going for a run, where's my trainers - it's a lifestyle, a way of life, and it's a mindset. I'll always have that and I think I'll always be itching for the big fight."
Froch admitted in January of this year that the thought of never fighting again had some appeal, saying it was "quite a nice thought".
An elbow injury forced Froch out of a planned March 28 fight against Julio Cesar Chavez Jr in Las Vegas.
At the time, Froch posted a photograph of his gloves hanging up on social media, sparking suggestions of a possible retirement.
Froch thought then that he would rediscover his appetite but reached the conclusion it was time to step away from the ring.
He vacated his IBF super middleweight title in February as he continued to recover from the elbow injury that scuppered the Cesar Chavez Jr fight.
"There's no greater feeling for me than standing victorious in the arena and I'm never going to get that again now, and I don't know where I'm going to get that feeling from," Froch said.
"I don't know where it's going to come; maybe it's not. That's what I'm turning my back on and that's what's going to be difficult to do, but there comes a time in every man's career where he's got to say, 'That's it, enough's enough'.
"I feel civilised now. I feel like Carl Froch the fighting machine is still in there - the fire is still in the belly - but it's been too long.
"I just feel like that fighting machine that I love so much and that I need to be to compete at the top level, I feel like it's been put away for too long, and I don't know if I can get hold of him again and go one more time. I really don't think I could."
Froch's fight promoter Eddie Hearn said: "He's always tried to be a positive role model and I feel he can give back a lot to British boxing.
"He's given a lot as well. You should remember Carl Froch for the fighter that he is, someone that never ducked anyone, something that gave the paying public value for money every single day of the week."
Hearn told Sky Sports News: "I've learned a lot from being around him. He's an inspirational guy, and he's not someone who's come from the Olympic background and he's been given the platform to go out. He's grafted for every single penny, every bit of success he's ever had, and for that you have to give him ultimate respect."
Groves paid a qualified tribute to Froch, lauding him as a "tough, strong man" but questioning whether he would have been good enough to hold his own against previous British super-middleweight greats.
Groves and Froch did not hide their dislike for each other in the build-up to their two big bouts and the controversial manner of the stoppage in their first fight clearly still rankles with the Londoner.
Groves told Sky Sports News: "Carl Froch was a tough, strong man, very tough, I don't know how he would have got on with those guys.
"I don't think he'd have beaten Calzaghe, Calzaghe would have been too quick for him. Him and Nigel Benn would have been an out-and-out war. Benn has a bit more skill and class about him but that would have been a great fight to watch.
"He's a tough man to beat, Carl. Sometimes you think you've got him and then a bit of controversy gets in the way. Sometimes you're boxing really well, you're in full control, and one punch can change a fight. There's plenty of fights of Carl Froch's that I've watched and thought 'he's losing this', or 'he's not going to get the win', and he ends up getting the win.
"There have been some great wars, some great fights to watch. He's always entertaining for the casual fan because he's happy to take a punch to land a punch."
And Groves, who has won two straight bouts since his second loss to Froch in May last year, said he hoped the pair could put their differences aside now that Froch had hung up his gloves.
"I'd love that (to be friends) because then he'd stop digging me out and lying about me when I'm fighting," said Groves.
"We don't need to be friends of course: I've got friends. But there's a rivalry when you're going to box and now that he's no longer a fighter that rivalry isn't there."