Where do you draw the line?

Today I have been thinking a lot about 'self''.
What does that mean, to be one's self that is? I know that the term self can be used very loosely and it covers a wide variety of areas so i'll be a little bit more specific. I've been thinking about where to draw the line. I have found that in order to live in the world today and live with people, you have to let go of some of the aspects that contribute to 'self'. So where do you draw the line? Where does compromising, being flexible, and living with people begin to take a destructive toll on the definition of self.
I am one of those people who puts the interest, desires, needs, and requests of others above mine all the time. It is part of who I am. It makes me the compassionate, loving, caring person that I am. While it might be annoying a lot of the time, I have embraced it, love it, and would not be any different. However, lately I have been feeling 'drained'.
'drained' : 1. feeling of exhaustion.
2. feeling like you are giving so much of yourself and are not getting anything in return.
3. feeling of emptiness, frustration, loneliness and sometimes anger mostly as a result of unreached expectations by people you love, cherish, care so very deeply for.
I love to give, love to give of myself, I would do ANYTHING for the people I love the most in this world, I would give ENTIRELY of myself for the people who make my world what it is, I would put aside my interests WHOLEHEARTEDLY for my family, my friends, my better-half. But sometimes I find myself in this place feeling nothing but 'drained'.
So where do you draw the line?