In reality, only in our textbooks is there a pedagogical but artificial separation between the short-term and the long-term or between the supply and the demand side.
The nature of mathematical economic models enhances this pseudo-difference as they feed the confusion between logical time (long-term in the models only means a logical interval until the final equilibrium) and the chronological time that we face in policy-making. In the historical chronological time, the long-term is no more than a sequence of short-terms.