Fallacy: Being difficult to attain makes a thing worth having.
Fix: The action must prove why the unattainable thing is necessary for the protagonist’s well-being.
Example: A protagonist’s goal is to be a size 0 for the reunion.
The assumptions: A dress size of 0 will provoke the desired reaction from former classmates, which is necessary for the protagonist’s well-being.
The story must prove the assumption.
This is a trap, obviously. There’s no way to prove that assumption, unless the story is a cautionary tale. The assumption can carry the protagonist to the midpoint, where she learns through action that what she desires is not the same as what she needs.
Examine those assumptions. They are the root of low stakes.