I know controlled breathing helps, but I can’t do it if I’m too amped up.
It’s more adequate when I notice I am escalating and recognize that I need to calm down. Being able to notice and recognize, though, demands I am already attentive to my own responses and relatively self-aware.
And no, even when done faithfully with the best timing possible and the best result possible, I am calm for maybe 5 - 10m before I start all over again – either the psychotic symptoms, anxiety, paranoia, or emptiness / sadness.
The best technique I have found is distraction. I spend most of my time trying to distract myself from what’s going on inside my head. That’s not healthy, but it works, until I try to go to sleep, or I have to go for a walk and I don’t have my headphones, or I am in any way “alone” with myself.