It happened to me more than once now, where I asked a "where is my mistake" type of question, feeling either that I'm really close to the correct solution or that I made some fundamentally wrong mistake and searching for some insight.
In the last instance (found here) I quite immediately after posting realized that my mistake was a trivial misunderstanding and there was no real knowledge to be gained from answers to the question. In some past instances, if I recall correctly, I had the simple mistake mentioned in the comment, giving the same overall effect.
What is the correct thing to do with such questions? Should I add the trivial detail I was missing as an answer and accept it or should I just leave it deserted as is?