It's bad to use other's things without their permission.
Sarah needs a ride to her friend Julie's house, but the only car there is her boyfriend John's, and he's at work.
Sarah wants to visit Julie.
Sarah calls John at work to ask if she can borrow his vehicle.
Sarah just takes John's car and drives to Julie's without asking.
John appreciates that Sarah asked, and he tells her she can use it.
John gets home from work and no longer trusts Sarah because his car is gone.