Tabitha should leave the movie if she is not enjoying it. The money she spent on the ticket is already gone—this is called a sunk cost. Continuing to watch just because she paid will only waste her time, which is also a scarce resource. The most efficient use of her resources is to spend her time doing something more enjoyable or productive instead of staying in a movie she doesn’t like. In other words, she should focus on the benefit of her time now rather than the money already spent.