play nice(It means to follow the rules and be kind and courteous when you're doing whatever it is you're "playing nice" in; to behave oneself in interaction with others, in particular refraining from instigating trouble, teasing or being cruel; it means to get along with and be nice to whoever you're supposed to "play nice" with. ART Vancouver)
treading on eggshells(To act with great care and consideration so as not to upset someone, some situation, etc.: The littlest thing tends to anger my mother, so I feel like I'm always treading on eggshells whenever I'm at her house.КГА)
step up to the plate(в отношениях; делать шаги навстречу. "No longer will you cling to relationships for the emotional security if the other person does not truly step up to the plate and treat you... " OLGA P.)
