Spinoza - Prop. XVIII

A man is as much affected pleasurably or painfully by the image of a thing past or future as by the image of a thing present. 

So long as a man is affected by the image of anything, he will regard that thing as present, even though it be non-existent, he will not conceive it as past or future, except in so far as its image is joined to the image of time past of future. 

Wherefore the image of a thing, regarded in itself alone, is identical, whether it be referred to time past, time future, or time present; that is, the disposition or emotion of the body is identical, whether the image be of a thing past, future, or present. Thus the emotion of pleasure or pain is the same, whether the image be of a thing past or future.

(Ethics, Prt III, Proposition XVIII)