I, and a lot of other people, can panic on demand. It definitely doesn’t mean we can stop on demand. At all. I know various things I can do to lower my heart rate and slow my breathing, and a few tricks to make my brain hyper focus on something harmless and calming, and I can often use those things to shorten a panic attack, but I can’t simply end it.
But enter a heightened mental state on command, sure! I don’t recommend trying, but you probably could too, if you have any sort of anxiety disorder.
All I have to do is focus on the thought of panic, the feeling of rising tension with no climax, recall the feel of a hard and fast heart beat, and bam! Might take me half an hour or more to come down again.