(Which is partly why I won't share the thought I had last night that made me almost collapse laughing. I shared it with one person, through e-mail. Only way I felt safe sharing it.)
Laughter can be a short circuit: it can quickly cut through a lot of your personality's layers and filters. And NOT laughing can be powerful. A few days ago I was waiting at the bus stop after work and this other guy tried to tell me a joke. I didn't hear all of it, but I heard enough to wonder why it was funny. So I just looked at him. He tried again. I kept a neutral face: not about to laugh, but also not about to start dissecting the joke and asking Why is that funny? Because then you look humorless, and I'm very (maybe overly) sensitive to that. So I acted a bit like he was speaking a different language. Which he kind of was. He realized he wasn't reaching me, and went to other subjects. Non-joke-y subjects.
Think about what makes you laugh. Enjoy thinking about what makes you laugh.