When there are two or more contradictory beliefs. Often, it is a contradiction between critical thinking and your actions, and you tend to hate and mask it when with others.
This is linked to the just-world fallacy and the survivorship bias.
The adults (likely rich and successful) having children would hate to
admit to their children that school was bad because the parents' brains
were not suited to say contradictory things: they spent many years
"learning" there, but most of it was boredom and frantically barely useful. Perhaps this
is why the children may have cognitive dissonance too? Because what
their parents said did not match up to reality.
In most actions, there is no "half do" - other than the sunk cost fallacy, some think leaving e.g., a degree half-done is a total waste! This traces it back to the fact that whether to hunt for an animal is either to kill or to be killed - so if you were to carefully consider animal ethics while also thinking about how much you need the protein and meat - you will die, so we evolved to decide quickly in heurstical thinking.