Before you request a car, look at the fare and the transit alternative for that hour. If the ride is for safety late at night, take it. If it replaces a twenty-minute bus you skipped from habit, the bus is the saving. The same pause helps with rental cars: compare the total with fees, not the headline daily rate.
As an illustration, two unplanned 18 rides each week add up to about 140 a month. Replacing one of them with a fare you already paid for, such as a transit pass, keeps the other ride for when you need it.
Start this week
The next time you open a ride app, wait until you have read the fare out loud. Then decide.