Olga, lose you cool means to lose your temper or self-control. Is that what спокойствие implies? I thought it was something like самообладение.

Uly, yeah, I know what it means, but I totally forgot the word самообладание! Thank you!

Yes, you can use спокойствие in this context, but самообладание is much better!

Cool! Thank you.

Thank you

выходить из себя