Master Sgt. James Haskell was an aerial gunner for most of his 21-year career in the U.S. Air Force. Now, he struggles with Post-Traumatic Stress Disorder and says putting on a happy face to get through a day is like wearing a mask. He is from Haverhill, Mass., and is stationed at Holloman Air Force Base, N.M. (U.S. Air Force photo by Master Sgt. Kevin Milliken/Released)