The amount of service that you can give to another is the degree to which you have given to Self. The fine line is

What you feel is an imposition by another, 
someone else may not feel at all. 
They may have experienced that level of
service so that it is integrated within Self
and they are not feeling imposed upon. 
Yet, that individual would then have another
point at which they would feel imposed upon. 
Thus it becomes important that you find your
own point between Selfless and Selfish.