Taking on responsibilities that properly belong to someone else means behaving irresponsibly toward yourself. You need to know where you end and someone else begins. You need to understand boundaries. You need to know what is and is not up to you, what is and is not in your control, what is and is not your responsibility.
I think that's what I love about writing, is the ability to try to, in a sense, take a vacation from yourself and try to enter the sensibility of another time, another character, another place.