If you are doing something creative, be it a drawing, a photograph, a movie or whatever, there will always be the feeling that the result isn’t what you had in mind.
You might come very close. You might are very near of what was on your mind when you started working on it. I guess, you’ll always find that little detail that was supposed to be different.
If we could ask Da Vinci if his Mona Lisa was exactly the result he had in mind I’m sure that he would have some points to mention that differ from his imagination. The same might be true for Michelangelo’s famous frescos.