Always double check if you're editing the right file
Have you ever been in a situation where you know you're doing the right thing yet the result is still wrong? Yes, I've been in that situation a lot of times, actually.
It may sound stupid to be editing the wrong file but believe me once in a while you'll found yourself in the same scenario. Editing in three different sites with the same file, who wouldn't be confused with that?
In the end, you'll just laugh at yourself just like I do every time. =P