The Other Person (OP)
Tristans and Iseults exist in abundance in real life. A man leaves in pursuit of the other woman, his Iseult. He believes that this is a woman who can perpetually fan the fires of passion and provide all his heart's desires.
How does it feel if a man gets his divorce and marries his Iseult? What then?
Denis de Rougemont writes in "Love in the Western World:"
"Will the lover with all his desires gratified continue to be in love with his Iseult once she had been wed? Is a cherished nostalgia still desirable once it has recovered its object? For Iseult is ever a stranger, the very essence of what is strange in a woman and of all that is eternally fugitive, vanishing and almost hostile in a fellow human being, that which indeed incites to pursuit, and rouses in the heart of a man who has fallen prey to the myth an avidity for possession so much more delightful than possession itself?"
Iseult, the other woman, will not have an easy life. From the moment she chooses to destroy a marriage and becomes involved with her Tristan, she settles for less than the best that life can offer her. She dons the role of the OP ("other person"), the usurper, and this gets assimilated into her picture of herself or self-esteem. This is specially so since every human being is possessor of conscience.