Cancer is ruled by the moon, and Leo is ruled by the sun. They can literally be as different as night and day. Leo may outshine Cancer in the drama department, but as long as Cancer feels secure, they won't mind a bit. At their happiest, Cancer will glow softly and Leo will shine brightly. You could say that night and day are two dramatic forces competing for the same "stage"—the sky—each one having a season to dominate. This sums up the eternal tension that follows Cancer and Leo, causing one to constantly surrender to the other.
Leos and Cancers need extreme amounts of approval and attention, and lose perspective easily without a full daily dosage. Both can also be bossy, Cancer in a "motherly" way (scolding and nagging), and Leo in an arrogant way (bulldozing and boasting). Between Cancer's mood swings and Leo's drama, the show won't stop. Leos are one-person starship enterprises—think J. Lo, Madonna, and Martha Stewart. Cancers have a few Jedi masters of their own—like Tom Cruise, Pamela Anderson and Mike Tyson. Both signs want to be the best (Leo publicly, Cancer secretly), and will fight for the number-one spot. In the ego department, this can be a surprising attack of the clones.