Two benefits of relationships would be both emotional and physical support that you could need in your life.
Explanation:
Emotional as in mental support, your significant other can lift your spirits and change your moods to make you happy. Having a good mental support system is always a great thing to keep yourself from becoming mentally ill.
Physical as in a good way to encourage someone to eat healthier or to try different diets or help change/stop unhealthy habits from starting or continuing. If your significant other is overweight you could help convince them to start eating heathier, participating in more physical activity, and of course start diets.
In My Last Duchess, the painting and the art represent something that is long gone, most noticeably, his love for art. He claims that he once loved art but now that love is gone and he hates it as much as it hates him.
