I like holding amusing thoughts.  Here is one.  Suppose you are incredibly talented and creative but you have the attention span of a chicken.  And you have to cross a road to, well, get to the other side.  TDD helps you do that by laying down a line of green beans across the road.

In midst of my first TDD run, I paused a little too long and ended up refactoring a little too wide and too deep.  Although the extent of the changes I made were about what I am used in non-TDD refactoring sessions, I immediately lost track of what I was doing.  It was as if I ran though several areas of Quake and getting overwhelmed instead of clearing one area and one monster at a time.  Restoring the green bar took a while and the fun/beat/rhythm dropped.  Once back in safe territory, I kept each step small and the fun was back.