I can definitely relate to that. Time and again I think about these cool shots that appear in my mind, but when it comes to putting pen on paper, the results looks less than stellar. I had also wanted to do a TF:Mosaic, but that looks to be in a perpetually planning (daydreaming) phase.
Also, I've realised that I am really lazy. I'd much rather do something far easier (e.g. look at awesome pictures that other people draw).