Consistency Theory - Why do we go back on promises I'm fairly new to the field of social psychology so forgive me if this sounds like a naive question.

I just read about the consistency principle - "Once we make a choice or take a stand, we will encounter personal and interpersonal pressures to behave consistently with that commitment. Those pressures will cause us to respond in ways that justify our earlier decision."

I have the question - exactly what kind of decision/commitment are we talking about? As in, how do we reliably identify a situation in which a person has made a decision/commitment such that he will now behave as per the consistency principle?

If the consistency principle is really so pervasive, then why do people often back out of promises? There are tons of situations when people don't honor their "commitment" towards other people (for example not showing up for some social event, or not showing up for a date, etc.)
There's no reason that consistency and promise-breaking can't both be pervasive.  In the first place, if 20% of the population always broke promises and another 20% always obeyed the consistency principle then we would still call it pervasive and we still have 60% of the population.

But an additional complication is that no person always breaks promises or always obeys consistency and most people do both at some point. We can imagine a scenario in which a politician could simultaneously break a promise (to a rival political force) and obey consistency principle (keeping the promise would have betrayed his base).  So the two aren't really contradictory since consistency principle doesn't require one to be consistent about everything always.