I don't know if it's faking as much as it's compartmentalizing. From an early age I guess I learned that my feelings were not important. So I learned to focus on something else whenever other people were around. A good example is my job. I've been told many times that others come to me for advice because I'm the voice of reason and logic. I've also been told that I'm perceived as being tough and hard. Truth is I'm depressed, I have low self-esteem, and I cry a lot. No one at work (besides my boss) knows the real me behind the mask.
The thing is that everyone has a "work" mode and real life mode. When I get to work, my personal life goes into a box and I leave it in the car.