Anthony Joshua says he remains "angry at myself" after losing to Oleksandr Usyk but "it's fuelling me every day".
Joshua, 32, surrendered the WBA, WBO and IBF heavyweight titles to the Ukrainian, 34, in September after just the second defeat of his career.
A rematch is "in the pipeline" and expected to be staged in early 2022, when Joshua aims to avenge that loss and become a three-time world champion.
"I know I can be better than that night," the Briton told BBC Sport.
"It's easier to say than it is to do, but within my heart and soul, my brain and body, I truly feel I've got a lot more to give.
"I'm angry. It's growing, but it's fuelling me every day."
"I think people still recognise me as champion, even though I haven't got the belts round my waist. They know I've got the capability of becoming champion."
Joshua won his rematch with American Andy Ruiz in 2019 to become a two-time champion and has been training with new coaches in the United States as he bids to win the titles back again.
"I had to make changes," admitted Joshua. "If you remain the same, you get the same results.
"I've got to look at myself, I can only be accountable for me. I'm angry at myself and the only way I can be in a better place is to get myself right by going out there and performing. It's going to be like this for a few months.
"I do things with a smile on my face, but behind that there's a lot of tension brewing and the only way to get it out is by training and performing."
Defeat by Usyk dashed Joshua's immediate hopes of a unification bout with Tyson Fury, who won his trilogy bout with Deontay Wilder in October to retain his WBC belt, but Joshua remains hopeful of one day facing his fellow Briton.
"When that fight happens, it happens," he said. "There's been one hurdle then another. I can't keep chasing what's not in front of me.
"What's in front of me is to become three-time heavyweight champion of the world, and that's the motivation."