Do you notice when you’re not breathing?
For me, I do, usually when I’m under some kind of timeline, whether that pressure is real or self-manufactured.
In the physical reality, the pressure you create in your head can act like just the same way that pressure from an external source might, as if someone were squeezing your diaphragm, preventing you from inhaling or exhaling.
It is even possible that this invisible pressure is stronger than any potential external pressure, because you create it yourself. Were an NFL offensive lineman to give you a bear hug against your will, he might break a few ribs, but, you would continue to breathe, albeit restricted.
So, the next time you notice yourself squeeze yourself out of breath, explore where that squeeze originated from. Was is real, external pressure? Or was it created unnecessarily by you, perhaps even due to some choices you made prior to that moment of feeling ‘squeezed’.