The king sits on a throne set on a stone slab floating in the middle of a rough sea. He holds a cup in his right hand and a sceptre in his left, and wears a fish-shaped pendant. On one side a fish leaps from the waves; on the other a ship sails past. The sea heaves; he does not.
The King of Cups is someone who governs their feelings — you, or someone near you. Not someone without feelings; someone who has them and is not swept away. They get an infuriating email and sleep on it before replying. When this card appears, the situation calls for generosity and calm, or you find yourself leaning on someone who has them.
Reversed, the inside and outside split. Calm on the surface, rocking underneath, and feelings pressed down too hard come out somewhere unexpected — silent all day at work, then unloading on the family at home. In another direction, skill with emotions gets used to move other people: gentle words that press on guilt to steer someone where you want them. That could be someone near you, or you.
Worth checking: is my calm right now the result of handling the feeling, or am I just holding it down?
Reading this card as 'don't show emotion' takes it the wrong way. The king has not put the cup down. He has not thrown feeling away; he is holding it as he sits on the sea. Feeling what you feel without letting it take the wheel — that is the balance here.
With Temperance, that balance becomes steadier still. Overlapping with the Devil, check first whether the power to handle emotion has slid toward control and manipulation.