I'm naturally bent to be playful during therapy sessions. Often, with counselees who find themselves stuck, I discover that humor in its appropriate time can make a gigantic difference in their progress. As one fellow therapist puts it, "play lubricates the process of change."
Here's what happens to me when laughing during therapy work. It energizes my approach to help people heal. Every counselee presents a life-threatening problem and its usually from a single or narrowing angle that keeps him or her stuck. Now, the simple maneuver of humor can look at an old problem from a different angle or from varied levels. That in itself can provide a form of psychological and emotional relief.
Now you know that I'm unusual. I like inviting people to go outside the box. When we meet up, be prepared for novelty, different ways of looking at life.