BOSTON » It’s not the belt he’s fighting for — he’s got eight of them tucked away in a closet at home.

It’s not a legacy he’s training every day for — that’s something he realizes others will decide.

B.J. Penn’s fight with Frankie Edgar in the main event of UFC 118 on Saturday night boils down to the same principles he had growing up in Hilo.

Every scrap was a chance to prove you’re the best. When you lose, the only thing to do was wake up the next day and not let it happen again.

"Me and my friends would always get into scraps and I’d always say, ‘I’m not the best, but I’m hard to beat,’ " Penn said.

"I really feel that about myself. I might not be the best every day of the week, but if you catch me on the wrong day, I’m going to show you something you’ve never seen before."

Edgar caught Penn on the right day back in April, earning a disputed unanimous decision victory that included one judge scoring the fight all five rounds for Edgar.

The debate left UFC president Dana White no choice but to make an immediate rematch to determine whether Edgar’s victory was legit or a fluke.

"The last (fight) was razor thin," the soft-spoken champion said. "Definitely gives me much more respect (to finish Penn). I expect a tough fight and to get that finish would be great."

To do that, he’ll have to beat the most successful lightweight fighter ever, whose motivation level will be at an all-time high.

Penn’s focus and dedication have been questioned multiple times, but recent history suggests losing is his biggest motivator.

Following his title loss to former welterweight champion Matt Hughes, he came back to destroy Jens Pulver. After he was dominated by Georges St-Pierre, Penn put on a clinic in takedown defense, earning an eventual submission victory over Kenny Florian.

He’s 4-1 all-time in fights coming after a loss.

"Besides everybody knowing (you lost) and you don’t want to talk to anybody, what hurts is when you’re sitting there and Dana is saying, ‘We’re going to announce something in a month that is going to blow your socks off’ and you’re like, ‘He’s going to announce something, and I’m not at the forefront?’

"When Dana guys are doing all these big plans, I want to be involved."

Penn’s 10-year relationship with White has taken more twists and turns than an M. Night Shyamalan movie.

Penn left the company as its champion following a contract dispute, only to come back years later after fighting in Hawaii and Japan.

The two made amends, but following the recent release of Penn’s book "Why I Fight," the two aren’t on speaking terms again as White has taken offense to comments made in the book regarding him and the UFC’s business practices.

"I don’t want to say anything bad about (Dave) Weintraub (the author), but things were written that I would never say," Penn said. "It’s sad to say, Dana is really bummed about it. I’ve tried to amend the situation and put everything back together, but it’s going to take some time."

To White’s credit, he didn’t let personal animosity get in the way of the fight that made the most sense.

"Never let those things get in the way of business," he said yesterday.

The business at hand is a title fight that doubles as a chance to avenge a loss.

For the 31-year-old Penn, who will compete in his 11th world title fight, the latter is just as important, if not more.

"After I beat Frankie Edgar, I know it’s UFC policy that I have to take the belt … but I don’t want to be labeled a champion.

"I just want to be labeled a fighter."