I don't know what you consider as "heavy weight" but last workout I did a 3x5 squat with 160kg and it was really mentally taxing. I do have some ways to prepare for a PR but I was sincerely hoping to get the opinion of the professional users of the forum, which I'm thankful for
Rep PR, put the weight on the bar, focus, get under bar and lift it.
For a max effort single there is more of a ritual.
~Training buddies load the bar and set bar height
~Chalk hands/back/whatever is sweating and will be in contact with the bar
~While standing over the chalk bowl visualize the successful lift
~Put on belt
~Fire up but stay focused
~Lift it!
Yes. This happens at a meet, not in training.
I'm convinced that the ideal mental approach to the bar varies on the athlete. Some people need lots of arousal and noise and others need to dial it down and internalize. Here's what I've found seems to help regardless of your 'rev type:'
Establish a ritual to your physical bar setup. Build in the habit of approaching the bar in the same way, in the same order, every time. Bring that same mental and physical setup to the bar in competition, just dial up the arousal as needed. Done this way, you have confidence in your approach, and it's easier to notice the small variations in stance/efficiency that creep up as the weight gets heavy.
As the weight gets heavier and the roaring in the ears gets louder, it gets harder and harder to focus on complex technique cues. Dial in your technique in your warmups, then pick either your most important cue or a generalized 'master cue' for your PR attempts and trust that the rest will happen. Depending on how I perform on the previous session, warmups, and opener (in a meet), my master cue for the squat has been either midfoot balance or aggressive hip drive. I try not to 'talk' these cues to myself or I spend more time thinking than acting. I try to feel my point of balance and feed the most accurate info to my instinct to execute as necessary.
If you're doing sets across instead of one heavy set or 1RM attempt, go for consistent and methodical rather than trying to Kaioken each time. The crazy-crash cycle is pretty exhausting.