To cheer up or regain one's energy/spirit; often used as an encouragement to someone (e.g. "cheer up").
失敗して落ち込んでいるなら、元気を出してまた挑戦しよう。
If you're down because of a failure, cheer up and try again.
元気を出して、今日は君のスピーチの日だよ。
Cheer up — today is your day to give the speech.
彼は病気から回復して、ようやく元気を出してきた。
He recovered from his illness and has finally started to feel better.