A relevant scene from The Hurt Locker: https://www.youtube.com/watch?v=3PgbNQU3cYo

In this scene, the character has just returned from a tour in Iraq defusing IEDs. The movie portrays him as a total pro in the battlefield, but stunned and anxious as he returns to civilian life. Great movie not just about war, but about the psychology of war and purpose.

Edit: here's a better dissection – http://www.cinemablography.org/supermarket-scene.html