It's all right to tell your former spouse, children, boss, family, or friends "NO". There will be no dark cloud of doom befall you. The sun will rise again, and this is a perfect opportunity for you to practice and learn to turn off those emotions driving you to do too much, give too much, and take whatever others are willing to dish out.
If you're going through a bitter divorce and custody battle, let your divorce lawyers handle the ugly messiness. That is their job, and they understand your stress and frustrations. They are more than capable of dealing with all the issues. You need to take care of your children, getting them and yourself through this new life adjustment.
Due to increased responsibilities as a single parent you may have friends and family who miss the carefree days you once enjoyed for talking and socializing. Maybe at one time your bosses' request for overtime was manageable, but now you have to draw a line. Even your children will test your resilience as the main disciplinarian. You have no choice but to set boundaries everyone will have to live with.
Here's a suggestion every single mom has trouble with - take some time for yourself with NO interruptions. On a daily, weekly, or monthly basis, schedule some alone time. This is not a time for Bible study, although prayer should be allowed, you are never bereft of the Lord. Grab a notebook and pen to write down thoughts, but don't use this time for planning. Fill your mind and notebook with positive, uplifting thoughts, release pent-up emotions, and cry out to your Father. Let this be a building up of your defenses and self-esteem.
Allow yourself to be pampered from time to time, eat right, exercise, get your hair done, and dress up once in a while. Most of all, just say NO!