All mommies tend to put everyone first and when you work outside the home, your boss is just another someone in that line of people who need something from you. When you are working full time, want to maximize the amount of time you spend with your kids, keep your home organized and dinner on the table it's often difficult to find time for yourself. However, it is so important to do. I've heard Dr. Phil say a number of times "if momma ain't happy, ain't no one happy." Whether or not you like Dr. Phil, the saying is quite true.
So, try hard to find time for yourself. If your spouse can watch the kids while you go out for an hour or two, have him do that. Perhaps you have friends that wouldn't mind you dropping the kids at their home (maybe someone in your shoes with whom you can later return the favor). If you have no one to help you watch the kids call in sick one day (or take a personal day), drop the kids at daycare, and spend the day alone. You can shop, go to a show or just lay in bed all day reading a book. Recently I joined a gym and get up in the morning at 5 am so I can run for an hour before I go to work. What a difference this has been making to my mood (and my waistline!).
It's often tough to give yourself permission to take time alone to recharge, but remember how important it is. Every time I do something nice for myself, I'm a much nicer person to be around.