A farmer living in the state of Song, about 1800 years ago, once saw a rabbit run across his field, into a tree stump, and die.

Delighted by the effortless meal, he abandoned farming and waited beside the stump for another rabbit.

And... waited. And waited. While weeds grew in his fields and his pantry got thinner.

Whoops!

That's why "guarding a tree stump, waiting for rabbits," is a cautionary idiom about ensuring your methods meet the fullness of your situation, and not just what is apparent.