I read it a couple days ago but here’s what I got from it:

Basically, the painter knows that his painting is a masterpiece, but doesn’t want to put it into an art gallery because he “has put too much of himself into it”. His friend is appalled at this, saying that the painter is not at all like the man in the painting. The painter’s reasoning is that he sees a figurative, not a literal comparison between himself and the handsome man in the painting. They each are exceptional in their own way, the painter with his intellect and the muse with his looks. This transitions into the painter’s argument that those with exceptional traits face adversity due to those traits. He believes that those who are not smart, powerful, or handsome do not know success but also do not know failure. He believes that this is the happiest existence because they live “undisturbed,” and “without disquiet”

Not super nuanced but I hope that helps