Become calmer than your previous pressure response.

You already know how you behave under pressure, because you have been there. The sharpness, the rushing, whatever your particular version is. That known pattern is a much better target than an abstract ideal of calm, because you can prepare for something specific.

Recall exactly what you did last time the pressure rose. Then decide on one small change for next time: a pause before replying, a walk before deciding. You are not aiming for serenity, only for slightly less of the old response.