I have always seen the King of Cups as a custodian of the emotional self. The one that has mastery (not to be mistaken with control) over all that they feel, to be able to sit with their emotions as they are, without judgement, to just make space for the expression needed at the time, for all emotions to come and go naturally.
Traditionally, water symbolizes all things emotion. And so the King, holding a cup in his hand, sitting amidst a choppy sea, looking out, unperturbed, represents the ability to allow emotions to surface as they need to. Even in turbulent or challenging times. Because that is the only thing to do with emotions. Let them be felt, so they can pass.
Our training in the world around us may be to deny the true state of our emotions, to feel them privately or not at all, to “control” them by pushing them back within, to overpower them in this way, to favour positive emotions over harder ones, to genderize them, label them, reject them. The King of Cups is a nudge in a different direction: to do whatever it takes to be custodians of our emotional selves. To let emotions arise, not so you can learn from them, work on them, fix them. But just so they can flow. This is probably one of the nicest forms of self-compassion and self-care.
If “eat your veggies” is what we tell ourselves to feel physically healthy, “feel your feelings” is what we should tell ourselves to feel emotionally healthy.