I composed myself, then walked on unhurriedly.

我定了定神，不慌不忙地向前走去。

《新英汉大辞典》

I took a deep breath and composed myself.

我深吸了一口气使自己镇静下来。

youdao

I tried to composed myself, forcing deep, even breath.

我强作均匀的呼吸，努力使自己镇静下来。

youdao