keep one's eye on the ball

/K IY1 P W AH0 N EH0 S AY0 AA0 N DH AH0 B AO0 L/
verb
  1. 1

    To maintain one's concentration fixed on one important theme.

Source: https://en.wiktionary.org/wiki/keep%20one's%20eye%20on%20the%20ball