The suite of cups, as a rule, is about feelings, emotions, intuition, sensitivity, imagination, joy and peace.  In the context of a relationship, the cups allow the soul to receive love.   When you look at the essence of water it is an element that mixes, moulds and flows.  It  can run shallow or it can pool off into great depths.   This is how a relationship will run its course, a couples feelings can produce anything from a superficial flirtation to the deepest and most powerful experience of a loving relationship.