Writers worth their ink need to be making some point with their story. Beneath your storyline, there should be a deeper message. It is a writer’s (or artist’s) job to present the human condition as they interpret it. So, once you’ve shaped the general idea, you should sit back and consider what it could be saying on a universal scale.
Consider Aesop’s Fables; each one is a tale that could be enjoyed on a superficial level by a child, yet there is a deeper meaning, or moral, which endeavors to teach the child some universal truth about life, i.e. being slow yet determined is often better than being hasty and fickle (Tortoise and the Hare).
A good place to seek inspiration is a list of proverbs. A proverb is usually a metaphor and encapsulates in simple terms, a lesson from the common experience of humanity. Here’s an exercise that might get you going: sit down and have a think about the specific meaning of the following and then go freewrite a story illustrating this philosophy.
Graveyards are full of indispensable people.
You can catch more flies with honey than you can with vinegar.
A little learning is a dangerous thing.
The belly has no ears.
Trees don’t grow to the sky.
A dumb priest never got a parish.
The only free cheese is in the mousetrap.
Eaten bread is soon forgotten.
The squeaky door gets the oil.