1. An imperative command telling someone to remain calm, relaxed, or undisturbed; to not worry or be anxious
Don't worry about it, just stay calm and everything will be fine.
Fica sossegado, que tudo vai dar certo.
2. An expression of reassurance or comfort to someone who is stressed or worried
Take it easy, there's no need to be upset about what happened.
Fica sossegado, não é para ficar bravo assim.