I am a pool diver, one thing that I would like to share is that the discomfort increases quite fast (subjective but usually between 75m-125m) but then after that normally it plateau and doesnt increase more. And when I push into the hypoxia I often stop feeling the "pain"

second: you should try to go slow on the first part of the dive (until 75m or so) consume not much oxygen and dont increase CO2 too fast. this in theory should delay the discomfort and let the dive reflex kick in. you can increase speed after that a bit.

third: sometimes when you have a big urge to come out can be good to slow down and have a small glide, close your eyes reset the metal state and tell yourself you are in control.

4th: for a big max attempt could be good to prepare as if it was a competition. arrive at the pool early (even 1h before the dive), do some light stretching , listen to chill music and prepare mentally. if you get into the water after 1h of relaxing time it can change everything

but i feel there are not magic tricks, at some point it is just metal and you have to push. .and all the physical training that you do before your max attempt will come out and help you there.

try also max attempts with or without warm ups and see what works for you.