Keep your chill
(to) keep your chill is to not break down mentally, or to not lose your temper. If someone keeps their chill, they are able to endure moments of high stress.
Jane: Hey, do you know how Kate is doing? I heard she's had issues with depression and it's breaking her down.
Brad: Don't worry about her. Kate kept her chill. She had some troubles with the breakup, but she didn't break down.
Bob: Oh no! I did not study for the science test tomorrow! I am totally going to fail, and then I have to re-do this year!
Tim: Keep your chill. Someone posted a great summary on the school website, you should be able to learn for it in a day.
Brad: Don't worry about her. Kate kept her chill. She had some troubles with the breakup, but she didn't break down.
Bob: Oh no! I did not study for the science test tomorrow! I am totally going to fail, and then I have to re-do this year!
Tim: Keep your chill. Someone posted a great summary on the school website, you should be able to learn for it in a day.