The importance of humor in ones work can not be overstated. It's really not funny. Humor is such an important part of play and that's pretty much what's going on in picture taking, isn't it? Even during the most somber missions with a camera, imagination and play are at work to find point of view, irony, story, symbolism, metaphor, originality, momentousness, everything. It may not specifically be humor driving the engine, but humor feeds the fire of imagination, at least for me.
I said to my wife, "Go hug that tree." So she did-- only from the back. The instant I saw her hands reach 'round-- click. it was funny but it was simple, it said love, it made the tree come alive, all of those things and more. So if you're getting too serious, buy a silly wig and go take pictures. I guarantee something interesting will come of it.