What is a good abstraction?

When writing a program, abstraction is a powerful tool.

Every abstraction has a benefit and a cost. Hopefully, the value > cost.

There are good abstractions and bad abstractions.

Good abstractions break things down into simpler steps that others can understand.

Bad abstractions may be brilliant but are nearly impossible for anyone but the author to understand.

Who are you optimizing for? Yourself, or everyone else?

This often tells the difference between a good and bad abstraction.