In the Four of Cups the emotions are stabilized. A relationship might be
comfortable, but it is fixed, the zenith is already crossed and the worth is taken
as granted. When there is no more risk, freedom and exitement are lost.
The 4 as the number of structure and reality implies a certain authority, it provides security and order. This might be useful when it comes to Disks, but emotions can't breathe with too much control, waters will foul when kept from floating.
Therefore, the Four of Cups is not quite the best choice ever, and it shows. Behind the bright glamour of the four golden cups the grey tristesse of emptiness is already lurking.
Drive: Emotional richdom, stability of feelings, love without risk
Light: Maternity, protection
Shadow: Possessive 'love', restriction of others in order to satisfy one's self, or just for wrong intentions