Think about this way

My Chinese boss used to tell me: you are working for yourself not for the company. The more you do the more experience you earn. But still you should set up a bottom line.

There is a white girl always take advantage of me, shift her responsibility to me. I took the stuff in but I gave her back after I learned how to do it, of course I have enough excuse to do so. Now I know her job very well but she knows nothing about my job. If the company want lay off a staff from our Dept, she will be first one. haha

Just my 2 cents.