What I was wondering lately is if the sunken cost fallacy and commitment devices are two sides of the same coin. Sometimes people need to abandond dysfunctional projects no matter how much they invested, on the other hand, motivating yourself to not abandon a good habit is hard and one way to do that is to sunken-cost-trip yourself, commitment devices like chains.cc, habits diary and so on work more or less that way.

This sounds a lot like that kind of second-order rationality that according to EY does not exist: these commitment devices work by focusing on an irrational argument ("don't break the chain now, look at what a good record you have so far") instead of a rational one ("it makes no sense to abandon this good habit now") because our brain is wired so that it takes the irrational one far easier...