David Haye insists that he will not be tempted to box on beyond his 31st birthday on 13 October.
Britain's WBA heavyweight champion meets IBF and WBO title holder Wladimir Klitschko on 2 July, and he admitted: "It could be my last fight."
Haye said even the prospect of fighting Wladmir's brother Vitali, who holds the WBC belt, would not alter his plan.
"I've always said that I am going to retire when I'm 30," Haye told the BBC's Sportsweek programme.
"If there's another fight [against Vitali] that can happen quickly then let's get it on," said the Londoner
"Otherwise, once I've unified the titles, there's nowhere else to go - I've always anticipated retiring and have adjusted my life according to that."
Haye turned professional in 2002 and set his sights on becoming a champion boxer when he first took up the sport as a 10-year-old.
"I cease being 30 on 13 October of this year," he added. "I've achieved what I wanted to achieve, and particularly after I've won this fight, unifying the division."
Haye claimed the WBA heavyweight crown from
Russian Nikolay Valuev
in November 2009.
David Haye Factfile
13 October 1980
25-1 (23 KO)
England Seniors 1998
The fighter damaged his hand in that encounter in Nuremberg.
Haye says that should he pick up a similar injury against Wladimir in their unification bout in Hamburg, there would be no return.
"If I damage my hand in the same way I damaged it against Valuev, hypothetically that would be my last fight," he added.
"I'm training with that in mind, that this could potentially be my last fight, so I need to make it my best.
"I need to be in better condition mentally, physically, spiritually than ever before and I'm not going to let the British public down. No way am I going to leave my titles in Germany."