Walking out of a bad movie halfway isn’t wasting the ticket. Staying is wasting the evening too.

Money already spent cannot be recovered by suffering through more of something. The ticket is gone whether you stay or leave, so the only live question is what to do with the remaining two hours. Staying in order to justify the cost simply adds the evening to the loss.

Look at what you are continuing only because of what it already cost. Ask whether you would start it today from where you stand, and let the answer rather than the receipt decide.