How can you influence your writing?

Yesterday evening I battled through the fog to my writers circle in St. Albans. We were having a workshop where we were actually asked to write. This doesn't often happen. More often than not, we hold manuscript evenings where we read and discus each other’s work. However this was not the case. The instructor had brought in a morose picture with a girl holding what looked to me like a giant bag of Fish & Chips. I found the picture quite depressing. Other members of the circle found they could make comic pieces from this image, mine was far from comic. Then after tea break we listened to a piece of music. More depression! The music actually made me angry and I wanted to walk out. I forced myself to stay and write something. What I wrote was powerful but angry and very dark. Much removed from the children's writing I love doing and want to achieve in.
We discussed how visual stimulus and musical stimulus can influence your writing. Many of the writers said that they might use this method to help them develop their work. For me, well, I think if I want happy thoughts and I'm feeling a wee bit down it might work, but I don't think I want to experience the dark side again.