Some years ago, I was attending a pastel workshop during which I had an "aha" moment. The teacher was doing a demo, painting a street scene from a reference photo. She was talking as she painted, and at one point said, "I don't know what that spot of blue is, but I like it, so I'm going to put it in." That offhand remark hit me like a lightning bolt. It doesn't have to be logical! How freeing! (Luckily, I didn't take it as a directive to follow the reference photo no matter what, which is rarely a good idea.)
The series that I'm working on (finished this one today... I think) involves a lot of randomness, as perhaps you can tell. The trickiest part comes near the end when it's time to refine the composition. The temptation to have it "make sense" is still really strong (that old left brain trying to exert control); I keep having to remind myself that I'm suggesting, not depicting. It doesn't have to be logical; it has to be beautiful.