No one thinks well under stress. Flight or Fright = Cortisol which shuts down deep thinking. Survival takes precedence.
So how do you handle stressful situations? You think about, discuss and prepare for difficult decisions.
The Army prepares soldiers for ambushes as an example. Trains soldiers to attack the ambushers rather than to sit helplessly and be slaughtered.
Drivers Ed taught us what to do when common emergencies happened. Brake and Steer out of danger. Recover from a skid. How to change a flat tire.
Daniel Levitin: “How to stay calm when you know you'll be stressed” is a great primer in preparing. He gives an example of a medical decision, and how to prepare not to lose something important.
There is a good likelihood something stressful will happen in your life. Do pre-mortems on likely stressful events to make better decisions.