forget martial arts, or sports in general... when my buddy beats me in Tekken or Street Fighter or Fifa holy shit I'd trash talk to the moon to get my rematch (since I was more often the winner).
I had to throwdown big too cause at this point they knew they had me hooked. One-sided incentive. If I won the rematch I got nothing. If they won they got a cash price, a personal stripper at the lounge, a fine bottle of single malt at the bar...
And that's just gaming. When we sparred, or fished, or played soccer/basketball or even just roll dice ('mexico'), shit got very serious and often ended in fights.
Guy things.
Obviously I understand why Aldo said "anywhere, anytime" because that was an emotional statement. He desperately wanted that one back, but that's why at that level, on a global stage, these guys have managers to overlook the business side of things.
Its no accident that his manager didn't inform him of the UFC's offer to have him fight Conor on 2 week's notice for no belt. Aldo would probably have jumped on it regardless, which would have been a bad move from a career-perspective.