Mindset can be created through patterns. Setup a patter you do each and every time you squat, whether it's warm up sets or work sets. Have three or more steps helps with the process. Watch an MBL hitter get ready for a pitch. They do the exact same thing every time.
The pattern can only due part of the work. Before you pickup the bar and walk it out, get your grip, close your eyes and tell yourself, "We are going to squat this X times." See if you don't start to see some focusing of attention intentionally on that set.
Look around for resources for athletes to get focus and attention.
I can guarantee you there is a weight in which you will walk it out and it will slap you in the face and get your attention, if you are not focusing!