The mind is the guardian of memories and fantasies, the past and the future respectively. Memories and fantasies come in two (and only two) varieties: good and bad. This means that all desires (related to keeping good memories and creating good fantasies) and all fears (related to avoiding bad memories and bad fantasies) come within the jurisdiction of the mind.

Unfortunately for the mind, the present moment is the only moment that is, in any sense, real. Moreover, in spiritual terms, the present moment is the only possible occasion in which we can meet God (or anyone else).

From Bread & Water, Wine & Oil by Archimandrite Meletios Webber (20).