Van Gogh was 30 when he wrote that in a letter to Theo. That was two years before he painted his first major painting and several more before he did anything most of us would recognize as van Gogh.

http://vangoghletters.org/vg/letters/let400/letter.html

(That website is a mammoth undertaking. Too bad the translations I've seen there are awful. They're scholarly, but read like wrung-out dishrags.)

Here's some more van Gogh (http://en.wikiquote.org/wiki/Vincent_van_Gogh):

I tell you, if one wants to be active, one must not be afraid of going wrong, one must not be afraid of making mistakes now and then. Many people think that they will become good just by doing no harm — but that's a lie, and you yourself used to call it that. That way lies stagnation, mediocrity. 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 mesmerises 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. Life itself, too, is forever turning an infinitely vacant, dispiriting blank side towards man on which nothing appears, any more than it does on a blank canvas. But no matter how vacant and vain, how dead life may appear to be, the man of faith, of energy, of warmth, who knows something, will not be put off so easily. He wades in and does something and stays with it, in short, he violates, "defiles" — they say.

And some more:

What am I in the eyes of most people — a nonentity, an eccentric, or an unpleasant person — somebody who has no position in society and will never have; in short, the lowest of the low. All right, then — even if that were absolutely true, then I should one day like to show by my work what such an eccentric, such a nobody, has in his heart. That is my ambition, based less on resentment than on love in spite of everything, based more on a feeling of serenity than on passion. Though I am often in the depths of misery, there is still calmness, pure harmony and music inside me.

And here is something that speaks to the struggle of the OP:

There is a great difference between one idler and another idler. There is someone who is an idler out of laziness and lack of character, owing to the baseness of his nature. If you like, you may take me for one of those. Then there is the other kind of idler, the idler despite himself, who is inwardly consumed by a great longing for action who does nothing because his hands are tied, because he is, so to speak, imprisoned somewhere, because he lacks what he needs to be productive, because disastrous circumstances have brought him forcibly to this end. Such a one does not always know what he can do, but he nevertheless instinctively feels, I am good for something! My existence is not without reason! I know that I could be a quite a different person! How can I be of use, how can I be of service? There is something inside me, but what can it be? He is quite another idler. If you like you may take me for one of those.