Decision making at the margin

I have just realised that most of my week is, well, was spent based on irrationality. I went and listened to classes because I paid for them, and therefore should go. However, what I paid was a sunk cost! I am basically paying for my degree. There are no consequences to not turning up to class. There are, however, consequences to not turning up to tutorials, so I better go to those. 

I can't believe I've been so stupid. I should allocate my time the best I can, not on going to class and pretending to pay attention based on some stupid sunk costs.

I love economics.