The tidal flux of human history (Vico’s Providence) tends towards forcing those who defend privilege to share more of the common wealth with more people. Those who support this movement are characterized as the left, progressive, those who resist it as the right, conservative. Psychologically, therefore, the right looks to the past, the left to the future. (Liberals try to have it both ways: to help the less fortunate while protecting their own advantage; thus they are ultimately conservative.)
Totalitarianism arises when either left or right attempts to purge their vision of the other – an idealized past that denies the future, an idealized future that denies the past – while also denying the present, because it must always be in between, in flux. It is the establishment of a dream-world that defies the real.