Be afraid that.

何も残せないまま時が過ぎることに恐怖しろ。
今日何も前進しないことに恐怖しろ。
何かしようと『思っている』だけでは何も残せないことを知れ。

Be afraid that time will pass without leaving anything.
Be afraid that nothing will move forward today.
You should know that you can’t leave anything just by thinking about doing something.