Rule; reinforcement.

Here is a similar snippet to the last one, except this time the first clause is short and punchy, and the second clause is more expansive.

In Somalia, family is everything; relationships are as essential as water and milk.

Notice how in the first clause Waris Dirie makes a big claim, almost like stating a rule.

In the second clause she expands on the rule, reinforcing it by using a simile: … relationships are as essential as water and milk.

In Australia, everyone learns to swim; public pools are as common as soccer fields.

In this school, effort is everything; hard work is the only road to success.

I can't stand horror movies; terror is one flavour of ice-cream I don't care to buy.

Write you own variation.
Write another one.