Hang in there 强调的是一种坚持，一定要坚持住，撑下去，别泄气

【例句】
Hang in there and you never know what you might achieve.
坚持下去，你永远都无法预料会有什么样的收获。

You better hang in there in order to get your college degree.
为要取得大学文凭，你最好还是坚持下去。