On the ball 机灵；反应快
I'm so glad that my assistant is always on the ball because I'm too scatterbrained to manage my schedule on my own.
Start the ball rolling 着手干，开始做
I think it will be easier to become comfortable driving now that I've started the ball rolling with driving lessons.
Pick up the ball and run with it
We had a very vague idea of what we wanted, but the marketing team just took the ball and ran with it.
Drop the ball 犯错误
I think she really dropped the ball when she decided to quit that promising internship.
keep your eye on the ball
We’ve got to keep our eye on the ball if we want to remain successful.