We all have the kind of days where nothing goes right. Everything you try to work on takes twice as long as usual, the computer crashes before you have saved what you were writing, your Internet quits while you are updating files, etc…
Recently I spent over an hour working on a theme I was creating and got nowhere. By the end of the hour, I replaced everything I had done with the original files and it felt like a wasted hour. When I went back to that project a day or two later, everything was fine and I finished the work quickly.