To act like a daystarxo means that you are extremely possessive and seek attention at all times. Extremely obsessed is one trait of being/acting like a daystarxo aka Mar. No one really likes to date daystarxo's because they constantly want reassurance and often seek to be the center of attention.
Ex: Stop acting like a daystarxo you seem like Mar.
Ex2: You're so two faced, what a daystarxo