In it's affirmative, as I mentioned above, it means to be gutted. But more commonly seen is the negative form and the imperative. Here are a few examples, followed by their English nuances. Enjoy.
- 例文1： いざという時に決心がくじけて、ボスに給料を上げてくれって言えなくなった。
- 英文： When it came down to it, I lost my nerve and couldn't ask my boss for a raise.
- 例文2： 何度も失敗しても、彼の意気はくじけなかった。
- 英文： Even though he failed many times, he didn't let it dampen his spirits.
- 例文3： 巨人に負けても、くじけずに頑張れ！シーズンは長いよ！
- 英文： So you lost to the Giants?!? Hang in there, you guys! The season is long!