The job you should have turned down

Every owner has one.

The customer who pushed on price from the first call. Wanted it faster, then wanted it changed, then wanted a discount because it took so long.

You said yes because the month was quiet.

Looking back, that job usually cost more than it paid.
The hours.
The evenings spent rewriting the same email.
The good customer who waited while you dealt with it.

The signs were almost always there in the first conversation. We just don't want to hear them when the calendar looks empty.

A polite no is not arrogance.
It is keeping room for the work you actually want.