When he takes the knife to the canvass the servants find him lying dead with a knife through is heart and "withered, wrinkled, and loathsome of visage." and the portrait "in all the wonders of his exquisite youth and beauty." p 349
The only way to get rid of a temptation is to yield to it. Resist it, and your soul grows sick with longing for the things it has forbidden to itself, with desire for what its monstrous laws have made monstrous and unlawful.
The 19thc hatred of Realism is Caliban's enraged reaction to seeing his own face in the mirror. The 19thc rejection of Romanticism is Caliban's fury at not seeing his face reflected in the mirror.