First of all, I must commend the buyer for having such high level of patience because If I was in his shoes, I’ll definitely panick. Is also cool you communicated with him to tell him your challenge at the moment.

getting nervous and trying to fix everything quickly only leads to frustration

This is actually the first thing that comes to mind at the moment because during that time everything seems to be unclear. You are out of your comfort zone faced with a newer challenge like 2 factors verification, I’ll definitely worry because of the buyer at the other end.

But like you said, it is preferable you calm down and go over things again to help tackle the challenges. I’ll definitely put this to practice but I’m praying I won’t be in such challenge you pass through…😊