If I've heard it once, I've heard it 442 times.
"Keep your eye on the ball!"
Sometimes it's from a tennis student who is yelling corrections to himself after missing a shot. Sometimes it's from a parent who's trying to give advice to a failing child. Sometimes it's from a TV tennis announcer who apparently thinks it's still 1978.
Regardless of where it's from, it's out there. And it's not losing steam.
Is that a problem?
Not at all. Unless you actually want to improve yourself.
I'll let you in on a little secret: nobody really keeps their eye on the ball.
Here's a picture of the greatest athlete of all time hitting a groundstroke:
Do you see where his eyes are? Nowhere near where he makes contact with the ball.
Furthermore, not only do athletes not keep their eyes on the ball, sometimes they don't have their eyes open at all! To wit:
Is his eye on the ball? Nope, his eyes are closed.
Do you see the craziness of this? For generations, people have been yelling this phrase at themselves and/or others, repeating a correction that isn't true and won't help at all.
So what's the big deal?
In the small picture, saying or believing something like, "Keep your eye on the ball!" will ensure that the mistake you just made will not get fixed. Keeping your eye on it won't make it go in the next time, and it might even cause more problems (slower swing speed, bad footwork, etc.). By adhering to a nonsensical instruction, a player is greatly hindering her progress and therefore will never reach her potential.
In the big picture, trying to improve by doing things that actually don't make us improve can seriously damage our lives. What if we overspend on a house we can't afford because a cliche told us that a house is a "good investment"? Or what if we end up divorced because we forced an early marriage because that is what we were "supposed" to do?
By following outdated, ineffective cliches, we're opening ourselves up to lack of improvement or possibly serious life problems. That's why we need to inspect every ounce of the "sound advice" we receive to make sure it makes sense and can make us better.
There are plenty of aphorisms that can truly make our lives better.
I'd like to add a new one: Keep your eye off the ball.