You can find many of his letters at the site
van Gogh's letter: unabridged and annotated.
“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 one succeeds and
one mustn't begin by despairing;
even if one loses here and there,
and even if one sometimes feels a sort of decline,
the point is nevertheless to revive and
have courage, even though things don't
turn out as one first thought.”