Baffled!

Sunk cost fallacy :
When one pre-orders a non-refundable movie ticket, the price of the ticket becomes a sunk cost. Even if the ticket-buyer decides that he would rather not go to the movie, there is no way to get back the money he originally paid. Therefore, the sunk cost of the ticket should have no bearing on the decision of whether or not to actually go to the movie. In other words, it is a fallacy to conclude that he should go to the movie so as to avoid "wasting" the cost of the ticket.

Today I realised that inspite of being aware of this fallacy and the underlying incorrect reasoning of "wasting" a sunk cost , I cannot ignore it.I am programmed to a mindset which says "You have wasted so much time and money on this,might as well see it to its end".But the big question here is :Is there really an end?Am I just spiralling downwards in the effort to "do justice" to the sunk cost i incurred ages ago?Am i now more vulnerable to a larger sunk cost?How does one know when to call it quits and escape form the clutches of this fallacy?