Notice how a lot of guys with supposedly strong chins hardly ever get hit cleanly on the chin. Take Jack Dempsey for example, in his bout with Gene Tunney, and as Gene tried he just couldn't land a clean hit on Dempsey's chin. Dempsey kept his chin tucked preventing Tunney's best punches from landing on the sweet spot. Dempsey knew what he was doing, all his bobbing and weaving, his slipping, and he didn't just come straight at you, he'd sidestep making you miss while getting in position to plant his own explosives. The same applies to other fighters that have reputations as rugged fighters, Julio Cesar Chavez, Roberto Duran, Rocky Marciano, they all knew how to take a punch, make themselves hard to hit, slipping and countering. Conditioning is a big factor too, I believe that the hard training that they went through made them all the tougher mentally when it was fight time. They could fight hurt, dazed, they knew what to do because they've practiced it constantly that it becomes instinctive to do so.

Anyone that is serious about going into fighting for the long haul should be wise enough to put in the time to master these moves and improve their physical condition.