How does your SO behave when he or she gets really stressed out?

I think it’s usually easier to see what someone else is doing than to observe yourself. I’m interested in finding out what people look like (facial expression and body language), as well as what their typical behavior patterns are when facing a lot of stress. I suppose that some people lose it (but what does that mean in terms of specific behaviors), and others might get even more tightly controlled, and others may hide in a shell. What does your spouse do? And for extra credit, how do you respond to that?