This is the type of statement that I find humorous. While I agree that the bills last year were great at running the ball and run defense was our biggest weakness, you can look at the panthers game as the same sort of mismatch. The difference was the level of intensity, and the willingness to compete. Emotion is such a huge part of sports, just look at the 12th man advantage for the seahawks, or the fact that Vegas gives the home team 3 points because of the emotional advantage the fans give the home team.
We humans, are emotional beings, and struggle to overcome the affects that emotions have over our actions. We can be affected in many different ways, but males are very goal oriented. Once a large goal is met there is a natural let down. If you look at some of the great generals of World War II, there have been books written on how some of them became depressed after the war because of the let down of having accomplished the biggest obstacle in their life.
Professional athletes are certainly no more prepared to overcome such emotions than war heroes. There is a reason why Vegas takes letdown games serious, and adjust their spreads accordingly. If you watched last year's bills game and think they had the same intensity as they had for the panthers (a non-division, even non-conference game), than all I can say is we were watching different games.