What's the idiom of being in a mess, being able to deal with it calmly and not panicking at all?

Relax: deal with, treat; Calm: calm and indifferent. As if nothing had happened. Describe taking care of yourself as cool as a cucumber. It also means treating problems with indifference.

It is easy to describe the calmness when dealing with difficulties or emergencies. Use "relax"

It is natural to describe a calm way to deal with difficulties or emergencies. It also means not caring about something. Use "relax"

Easily describe how calm you are when dealing with difficulties or emergencies. Use "relax"

Generosity means showing generosity and calmness in a dangerous situation.

Relax: no hurry, very calm; No hurry: no hurry. Take your time and calm down.