Acer and Jim are spot on John. I will add that sometimes you just have to give a project a break and get away from it for a while, go work on something entirely different and get your mind off of it. When you come back to it my bet is that it will instantly fall into perspective and you will immediately know just how to proceed, and then do it. Also, knowing when to stop is important, that is, there comes a point in the execution of a design, illustration, project that is a natural "this is done" moment and any more messing with it will only degrade it. Realizing this moment is as important as the moment when it all clicks and you know just what you are going to attempt.
I am not telling you to stop, I am only giving a general guide to how these "art" projects go as I know it. There is inspiration followed by sketching and a general work up to realizing the design. This is followed by commitment to a final design leading to a careful layout, whether it is on paper, canvas, a building or a gunstock. Then comes the second thoughts and nit picking yourself which is often times just a manifestation of anxiety and not really productive because your original idea usually turns out to be the best of you and you've already tweaked it during the sketch phrase. Go with it. Then the work of actually doing it, and many more times than not it is good, if not great.
Success!
Next, and this always happens - comes a depressive state to one degree or another, you are spent mentally but you recover rapidly and the next thing you know you have another gun to build, or canvas to paint. And then, this too always occurs - after some time has passed and you've more or less moved on and are deep into something else you happen upon that gun and spot your "art" and tell yourself "Jeez, that ain't at all bad, did I do that!"
Yes.
Dave