Here's what happened:
The moon floated down from the sky and hovered in front of me. The moon was really crazy looking in this dream. It was full of weird crystals and patterns and it was glowing in a really odd way. I tried to make a grab at it while it was near, but it floated away as soon as I began to show any interest in it. I chased that moon all over dreamland and was eventually able to catch it, but as soon as the moon touched my hands, it began to melt. I felt incredibly sad that I had ruined the moon; I really wished that I had never even tried to pursue it in the first place.
Since dreaming this up, I've always interpreted the moon (this dream only) to be a metaphor for failure, or at very least it represented something similar to a goal that was never achieved.
On the brighter side, the painting itself is no disappointment. Finally, after seven or eight years, I can cross this off my list of things I've been meaning to paint.