On Setting Boundaries...

I know we've broached this subject before, but I thought it was important to revisit.  Mostly because I am realizing how guilty women are made to feel when they say "no."

Please correct me if I'm wrong, but do we women start policing each other and how much we've sacrificed with our jobs, families, and relationships?  I feel this, "Well, I did it so you should have to now," mentality permeating my everyday life!  I know I sound naive, but I've had the privilege to work in some relatively martyr-free environments in my day...and I think it spoiled me!

So how do I draw my proverbial line in the sand without seeming like a laze or unambitious?  Is there any happy ground?  I feel (many, not all, of course) men are given respect when they say something conflicts with their schedule, but a rationale must be given from a woman.  What gives and how do we fix it?