This is the bias behind, "I can't cancel — I've already paid!"
That money is gone whether you use the service you paid for or not, so it shouldn't influence your decision. The same principle applies to everything from the failing business you've financed to the standing-room-only concert tickets you bought before you broke your foot.
By focusing on the past and refusing to let go of money that's already gone, you could trap yourself into spending even more.