Bill Johnson travels from the future to affect important political change at moments of crisis, but each time he makes a change, he also forgets all personal details about himself.
But each time you intervene, no matter how subtly, you change the future from which you came. You exist in this time and outside of time and in the future, and so each change makes you forget.

Variants

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  1. “Crisis” by James Gunn, in Analog, March 1977.
    2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . written by James Gunn