Mate the very best of shooters make mistakes all the time. I have seen some of the worlds best shoot on the wrong target, a competition ending score-wise mistake for them. There is so much to concentrate on its nearly impossible not to make a mistake until you have a routine well ingrained and even then things happen that put you off.
I often forget to set my Ocular focus as I have to wind it in to get the bolt in and out which must be done before getting up from the mound. I have to wind it all the way out then a 1/4 turn in. At least its not one that has the lock rings.