I think one good way to get control of that holy shit moment after unracking is to do heavy walkouts and then re rack.
last year, I used to have my holy shit moment even before unracking, as I looked at the loaded bar and all those plates. The main factor for me to get mentally focused on the cues and not the iron was the Crew. I just feel very comfortable with them. I always seem to do my best squatting with Brian, the crew leader, spotting me. I think its because I respect him as much as the iron.
In Vegas, I of course missed my opener of 375, and in the meantime got a sprain in my quad from squatting on carpet. I then proceeded to get my 405. This is because I already had my holy shit moment and all I could think of is that I was not going to go home without my beloved 405 squat. I simply had 1 zillion percent focus on that and forgot about getting nervous or anxious.
I think you just need more time to learn how to get into the right headspace when squatting. Like you said, you have only been doing it 2.5 years or so.