Do you know why lions don't hunt field mice?

Lions are carnivores. They eat giraffes, antelopes, warthogs. Sometimes, lions go weeks without eating anything. Yet, even a lion starving to death shouldn't hunt for field mice. And there's a simple explanation why:

For a lion, hunting mice burns more energy than it would retrieve from eating them. A lion hunting field mice would starve to death.

I've seen humans hunt mice, too.

However, the mice we're hunting aren't small, fluffy, mammals living on the prairie - they are projects requiring much effort for small rewards. If we only pursue these projects, we ultimately suffer the same fate as a lion hunting field mice:

We run out of energy.

Instead, we should be hunting antelopes

Antelopes have the opposite effort/reward ratio of mice.

An antelopes contains more calories than a lion burns hunting it. In other words, lions hunting antelopes gain energy. And I've seen humans hunt antelopes, too.

Antelopes are the projects requiring more effort, but with a large potential pay off.

It should be noted, pursuing antelopes is by no means an easy endeavor. A lion can need as much as 10 attempts to catch an antelope. Yet, because it knows the reward will outweigh the effort, the lion doesn't give up on its prey. And neither should you.

Thus, whenever you find yourself busy, you should ask yourself:

Am I hunting antelope or field mice?