The period of youth; while one is young (often used to recommend doing things early in life).
若いうちにいろいろな経験をするべきだ。
You should have a variety of experiences while you're young.
若いうちから英語を学ぶと上達が早い。
If you start learning English while young, you'll improve quickly.
若いうちの苦労は将来の力になる。
Hardships in youth become strength for the future.
若いうちは体力もあるので無理が利くが、無理は禁物だ。
While you're young you have the stamina to push yourself, but you shouldn't overdo it.