The Knight of Cups is all about feelings and exploring them. The illustration on the card is from an event in St. Johns life. He was ordered by the Emperor Domitian to drink poisoned whine. When John picked up the cup, the poison changed in a snake and departed from the cup.
It was a fine day really, a very fine day, but I was not feeling very fine today. I was emotionally at my end. This resulted in me being busy all day with changing the poison in my cup to a snake, so it could depart and I could enjoy this fine day more than I did. I think it is gone now, but I am not sure, and the evening is not over yet.