I always smile or chuckle as I'm recounting terrible things that have happened to me. If I'm telling my therapist about how bad I feel, I will usually look down and smile to myself. My sister is the same way, and we've been through a lot together. My therapist is aware of this and understands that it's my way of dealing with it, so I haven't had to explain that to her. She will just listen with a thoughtful expression. I only realized I do this as a defense mechanism because I had a psychiatric nurse who pointed it out to me.