keep one's eye on the ball

Idioms  

1. Remain alert and attentive, as in The research director told her students to keep their eye on the ball when it came to accurate footnotes. This expression alludes to numerous sports in which players must watch a ball's path. [c. 1900]

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Example Sentences

He is not against missiles, though sometimes quoted as being so, but he feels that in air warfare it is always necessary to keep one's eye on the ball, not on the distant future.

From Time Magazine Archive