Fetching details from the dictionary...

to calm down; to compose oneself; to regain presence of mind; to relax
to calm down; to settle down; to die down; to become stable; to abate
to settle down (in a location, job, etc.); to settle in
to be settled (of an arrangement, conclusion, etc.); to be fixed; to have been reached
to harmonize with; to harmonise with; to match; to suit; to fit
to be unobtrusive; to be quiet; to be subdued
深呼吸をして気持ちを落ちつかせた。
I took a deep breath to calm myself down.
新しい環境にようやく落ちついてきた。
I've finally settled into the new environment.
騒ぎが落ちついてから外に出た。
I went outside after the commotion calmed down.