La Vie à l'envers (1964)

A Paris real estate developer feels compelled to withdraw from his seemingly perfect life into a world of his own. Is the man going insane? By conventional standards, maybe, but it's clear that the life he's fleeing is madder still from his point of view, and since that point of view is unfailingly witty and astute, we even come to accept his delusions as more "real" than reality.