Anthony Joshua says he chose to “reinvent” himself after defeat by Andy Ruiz Jr and feels “different” going into Saturday’s rematch.
Joshua, who lost his three world heavyweight titles to Ruiz on 1 June, says he has decided to “check” his approach after a first defeat.
“There is fire in the belly,” the Briton told BBC Sport in Saudi Arabia before the fight at the Diriyah Arena.
“There are things I have had to do to take me to the next level.
“I am confident I can be victorious and when I am I will tell everyone of how I went wrong.”
Rumours circulated about Joshua’s condition in the wake of his shock defeat by Ruiz at Madison Square Garden.
Word from his camp is that he has delivered some of the most impressive sparring of his career in recent days.
There is also a feeling that the additional sparring partners he has used – including Mexican Elvis Garcia to offer some stylistic similarities to Ruiz – have raised his level.
After speaking to BBC Sport a short drive from the hotel complex where both he and Ruiz are staying, the former champion was scheduled to work out for the second time on Monday at his training base, the British Embassy in Riyadh.
“I do feel different,” Joshua, 30, added. “I feel confident, I believe. I have been boxing since 2008. It’s almost like it’s been given to me. Now I am back to the days of being younger, striving.
“The question I have to ask myself is, ‘after the fight am I going to keep that same attitude?’ I have to stick to it and that is what will take me on to the next level.
“I am a challenger. This is my chance at the heavyweight championship of the world. The event starts when I am victorious. Then I will tell you about my story, what I have come through, the obstacles.”
Royal appointments, hotel gyms and a cool Ruiz
Joshua revealed he has sought advice from former world champion Wladimir Klitschko and wishes he had done so sooner, adding: “For someone who is going through success now, who is winning, definitely check yourself.
“I have had to check myself and reinvent myself not physically, mentally.”
Both fighters met Saudi royalty and a vast number dignitaries after media commitments on Monday.
It was striking how demand for Ruiz was far higher than before their first bout, where he stunned the sport by stopping Joshua inside seven rounds to take the IBF, WBA and WBO world titles.
Ruiz, 30, appeared relaxed despite countless media requests. The Mexican is training at a custom-made gym set up underneath the hotel in which he is staying.
Many have questioned if he has remained driven given the rewards of his success, which have included a lavish new home, a Rolls Royce and high-end jewellery.
“I have been enjoying life. This is just the beginning,” Ruiz told BBC Sport.
“I sure haven’t stopped smiling. I have been so happy how my life has changed for my wife, my kids, my whole family. I am blessed with all that came my way.
“All of the pressure is on him, not on me as I followed my dream and made it come true.”