Come on, he thought, baring his teeth in the darkness—come on. Is that the best you can do—is that all you can hit me with—a moose and a tornado? Well, he thought, holding his ribs and smiling, then spitting mosquitoes out of his mouth. Well, that won't get the job done. That was the difference now. He had changed, and he was tough. I'm tough where it counts—tough in the head.
In the aftermath of the moose attack and the tornado, in Chapter 16, Brian resolves to overcome the setbacks of the day. While the rapidity of these events and the seriousness of their consequences baffle Brian, he immediately takes action to remedy the situation and to restore what has been lost. He rises to the challenge the day presents, and this quote certainly attests to that. He also recognizes here that his mind is the most important element to survival. He has learned this lesson in earlier incidents in the book; here he confirms it and uses it to build up his resolve.