頑張らないと

have to work hard

→ 頑張る
phrase Rare #32,394
have to work hard A shortened form of 頑張らないといけない or 頑張らないとだめ, meaning that one must try hard. Depending on context, it can also mean “if I/you don’t work hard.”
JA: 試験に合格したいなら、もっと頑張らないと。
EN: If you want to pass the exam, you have to work harder.

まだまだ頑張らないとダメだけどね

I still have a long way to go, though.

— 甘い生活 (1960)

次はもう少し頑張らないとダメだ

You’ll have to try a little harder next time.

頑張らないと落ちるわよ

You’ll fail if you don’t work hard.

彼はもっと頑張らないと何も成し遂げられないだろう

He won’t accomplish anything unless he works harder.