I thought of this too, I read it in Sum - Forty Tales from the Afterlives

It is not life that is a dream; it is death that is a dream.

You now recall that your dreams always had background characters: the crowds in the restaurant, the knots of people in the malls and schoolyards, the other drivers on the road and the jaywalking pedestrians.

Those actors don’t come from nowhere. We stand in the background, playing our parts, allowing the experience to feel real for the dreamer. Sometimes we listen and pay attention to the plot of the dream. More often we talk among ourselves and wait for our shift to end.

This is not a job choice but indenture: you owe the same number of hours of service as you spent dreaming during your lifetime.

pdf: https://cpb-ca-c1.wpmucdn.com/myriverside.sd43.bc.ca/dist/2/3627/files/2018/01/Sum_-Forty-Tales-from-the-After-Eagleman-David-2dspl4a.pdf