In "A Sketch" by Christina Rossetti, she aptly captures the essence of the man she is love with. What essence of her lover is she referring to?

In the poem, "A Sketch" by Christina Rossetti, it talks about the blind man that she fell in love with. The man was not physically blind. However, he was gullible and ignores the whole and focus on the smaller things. Because of this, he fails to see the other important parts of the whole.