Ohhh this was a hard message for me to learn in my youth. I wanted to be a friend to everyone and ended up being a doormat to a lot. It was hard to learn to say no. I ended up looking like a ... well you know what. But I realized I did not have to sacrifice myself for others. Also if someone wanted me to sacrifice who I was, then they really were not a friend in the first place!
PS there is times on ones life where you are called to give above and beyond yourself but that is a specific situation. Not a full time thing.