If you work in a factory making widgets then in eight hours you’ll have some amount of whatever you’re making to put into boxes and ship off to China, or wherever they’re sold. If you mow grass for a living then you can look at a lawn and be satisfied you’ve beheaded enough blades to earn your pay. A highway worker can pave a road and see the results, and be happy the road is smooth.
But writing means nothing more and nothing less than throwing dice where the pips are obscure, and the wager unknown. A day’s worth of writing might mean you merely discovered what part of the plot does not work at all. A finished piece of work may hold no one’s interest. A novel a writer devoted a lifetime into finishing may not sell at all, not one copy, except friends and family, who are just happy it’s over and done with.
Accept this. Live it. Take your work, print it out, and burn it, for the heat and light from the flames might be the only useful thing all your devotion to the Muse ever produces.
Then realize it doesn’t matter if it’s never loved or appreciated, or printed, or sold, or even seen by another living soul.
And get back to writing.
Heat and Light.