He turned himself into an artist by acting like an artist and going through the motions by turning out mostly bad innumerable rough sketches, day and night.
In Van Gogh’s own words “Just slap anything on when you see a blank canvas staring you in the face like some imbecile. You don’t know how paralyzing that is, that stare of a blank canvas is, which says to the painter, “You can’t do a thing.” The canvas has an idiotic stare and mesmerizes some painters so much that they turn into idiots themselves. Many painters are afraid in front of the blank canvas, but the blank canvas is afraid of the real, passionate painter who dares and who has broken the spell of ‘you can’t’ once and for all by getting to work and painting.”
It was very difficult at times, but he believed nobody can do as he wishes in the beginning when you start but everything will be all right in the end. Each day he made every effort to improve because he knew making beautiful paintings meant painstaking work, disappointment and perseverance. In the end, Van Gogh produced 2000 works of art between 1880 and 1890 (1100 paintings and 900 sketches). That’s 4 works of art a week for a decade, and he didn’t start making art until his mid twenties.
More here. And here.