I do it myself and I see it countless times on the internet in postings and responses to postings:
failure to completely read something and every little word of it
Before you react to a document, interpret it, analyze it, and decide “where to go next,” make certain you have read every line of the document. Don’t just react to the “big” obvious things as it often is the details that seem trivial that can be the most important.
Better yet…don’t react immediately at all. That’s when some of the biggest mistakes are made and the biggest clues overlooked.