Hell man, he's been getting beaten up by defensive linemen and linebackers for what, 13 years? Add that too all of the attention that concussions are getting and I can see why he could lose some of that drive.
I see how we as fans, rabid fans in some cases, can be angry and want to throw rabid wombats at the guy. I get that. I think he has proven he is indeed a warrior, just one who has realized his time has passed.