George Groves goes into his fourth world title attempt admitting defeat could mean the end of his career.
The Briton challenges challenges Russian Fedor Chudinov for the vacant WBA super-middleweight title at Bramall Lane on Saturday after three previous unsuccessful world title shots.
Groves [25-3, 18 KOs], 29, has rebuilt his career since a split points loss to Badou Jack for the WBC belt in September 2015, which followed back-to-back stoppage losses to Carl Froch.
"Training hard does things to the body that does take it a little bit longer to recover, getting the weight off, you age a little more after the sessions," said Groves.
"It's all good but yes it is now or never. I have a little baby at home, 10 months, I want to spend some time home with him so the sooner I get this cracked the sooner we are all on our way.
"There's certainly a lot of things I want to achieve before I hang up my gloves so there's no more time to be wasted. Ultimately, this could be my last fight because how many chances can one guy have?
"I believe this is the best opportunity for me to achieve my dream and become world champion. Time is on my side. I had a good year last year, and I'm in a good place. I've put in the work, and now, I need to make this count.
"Everything that's happened in the past has just made me more determined. I know the pressure is on, and I can't afford to make any more mistakes. This might be my best chance to win a world title, but it could also be my last."
As well as dealing with the pressure of a career-hinging fight, Groves has been affected by the condition of his last opponent Eduard Gutknecht.
Gutknecht collapsed into a coma and need emergency brain surgery following a punishing points defeat to Groves in November. Gutknecht has never regained consciousness, cannot talk or walk and his family have mounting medical bills.
Groves, who has won four fights since working with trainer Shane McGuigan, has had support from Kazakhstan-born and Germany-based Gutknecht's family.
But the Londoner admits Gutknecht's condition is difficult for him to live with.
"It's a horrible thing, I struggle with it, my wife struggles with it," Groves told the BBC.
Chudinov (14-1, 10 KOs), 29, lost the title he fights for on Saturday by a disputed, majority decision to Felix Sturm in February 2016 and the Russian has not fought since.
Sturm later tested positive for the banned anabolic steroid stanozolol and then vacated the title before he would have been stripped of the belt for the failed test.
Groves rates his opponent who comfortably beat another Londoner, Frank Buglioni on a previous visit to the UK in September 2015.
"Chudinov is a good opponent," said Groves. "The belt is vacant because he lost his last one but he was a bit unlucky in that fight. There are still some unknowns about him. We haven't seen how far he can be pushed, but I know I'm capable of beating him.
"It's up to me to deliver. I want to be world Champion and I want to be involved in some huge fights. I know I'm good enough, and with Shane in my corner, I'm back to my best, and ready to make to make it happen."
Victory for Groves would open up the possibility of a world title unification clash with his bitter rival James DeGale, the IBF champion who he beat on points six years ago.
A DeGale-Groves match up is perhaps the biggest fight in British boxing outside of the heavyweight division since the prospect of welterweights Kell Brook and Amir Khan ever meeting is becoming increasingly unlikely.