What can make any mare (and not mare only) happy?
Compliments of course, all mares love compliments ;3

And Valentine's Day is definitely is one from most happy days for princesses :D

P.s. Quick sketch by super old idea which i decided to draw only now^^
P.p.s. Just random thought:
Interesting, who from princesses getting the most amount of cards, and how other princesses looks on it... Do they feels...envy?
I think this could to be a nice idea for comic)