If the artist does not throw himself into his work as Curtius sprang into the gulf, as a soldier leads a forlorn hope without a moment’s thought, and if when he is in the crater he does not dig as a miner does when the earth has fallen in on him; if he contemplates the difficulties before him instead of conquering them one by one, like the lovers in fairy tales, who to win their princesses overcome ever-new enchantments, the work remains incomplete; it perishes in the studio where creativeness becomes impossible, and the artist looks on the suicide of his own talent.

[Si l’artiste ne se précipite pas dans son oeuvre, comme Curtius dans le gouffre, comme le soldat dans la redoute, sans réfléchir; et si, sans ce cratère, il ne travaille pas comme le mineur enfoui sous un éboulement: s’il contemple enfin les difficultés au lieu de las vaincre une à une, à l’example de ces amoureux des féeries, qui pour obtenir leurs princesses, combattaient des enchantements renaissants, l’oeuvre reste inachevée, elle périt au fond de l’atelier où la production devient impossible, et l’artiste assiste au suicide de son talent.]

Honoré de Balzac (1799-1850) French novelist, playwright
Cousin Betty [La Cousine Bette] (1846) [tr. Waring (1899)]
    (Source)

Curtius is the young Roman patrician, Marcus Curtius. In 362 BC, a chasm opened up in Rome's forum, and soothsayers proclaimed it could only be filled by Rome's greatest treasure. Curtius mounted his horse and leapt into the chasm, which then closed over him.

Alt. trans.:

• "If the artist does not throw himself into his work, like Curtius into the gulf beneath the Forum, like a soldier against a fortress, without hesitation, and if, in that crater, he does not work like a miner under a fall of rock, if, in short, he envisages the difficulties instead of conquering them one-by-one, following the examples of lovers in fairy-tales who, to win their princesses, struggle against recurring enchantments, the work remains unfinished, it expires in the studio, wher production remains impossible and the artist looks on at the suicide of his own talent." [tr. Raphael (1992)]
• "If the artist does not fling himself, without reflecting, into his work, as Curtius flung himself into the yawning gulf, as the soldier flings himself into the enemy's trenches, and if, once in this crater, he does not work like a miner on whom the walls of his gallery have fallen in; if he contemplates difficulties instead of overcoming them one by one ... he is simply looking on at the suicide of his own talent." [Source]
• Original French.