Nobody expects professional athletes to look thrilled to be alive constantly. After all, money and fame aren't everything. These guys are some of the biggest competitors in professional sports, and it shows on their faces at all times.
These guys need to take a lesson from Cole Hamels, a guy who is a huge competitor but also looks like he appreciates the fact that he's married to a model and playing professional baseball for a living!
Cheer up guys! Keep the intensity and the desire to be the best, but try to look like you're happy to be there every now and again.