Jean-Baptiste-Camille Corot said this quote

“ One should embrace the artist's profession only after recognising in oneself an intense passion for Nature and the disposition to pursue it with a perseverance that nothing can shatter - thirst for neither approval nor financial profit. Do not be discouraged by the censure that might fall upon one's works - one must be armoured with a strong conviction which makes one go straight ahead fearing no obstacle. An unremitting task […] an unassailable conscience. (From a sketchbook of 1847). ”