expression, ichidan verb
brace oneself; pull oneself together; focus one's mind
Used when someone consciously tightens their mental or physical focus, often before a challenge or after a lapse. Implies a deliberate effort to become more disciplined or alert.
試験の前だから、気を引き締めて勉強しなさい。
Since the exam is coming up, pull yourself together and study.
彼は気を引き締めて、最後の一球を投げた。
He braced himself and threw the final pitch.