If you are a stepparent, I dare you to finish that sentence. And to post the sentence online, for all to see.
I have not yet written openly about being a stepmother of a teenager, or how that relationship effects my marriage, my sanity, or my patience in parenting my own two small children. My feelings are too raw. The emotions are too big. The ramifications too high. So what follows is my restrained first attempt at the matter.
Before I became a stepmother, I read a self-help book on the topic. One line sticks in my head: "Being a stepmother can actually be a joyful experience." I believe the possibility is there, and that many factors play into whether you reach "joyful" or not. The biological mother and father play major roles. They have the ability to undermine and sabotage or help create a positive situation. The attitudes and personalities of the stepmom and the stepchild are, of course, also important.
I am pessimistic about getting to "joyful" if the child wishes their mother and father would get back together. Ditto when the stepmother is the primary parent to make rules, assign chores, and call attention to and enforce violations.
So what do you do? What comes next?
I guess you just keep on keeping on. You try to stay present with the other joy in your life and be the best mom you can be to your own children and you work on yourself as a person. You work on your own mindfulness. And I guess you never give up hope on getting to joyful. And you take respite in the reality of joint custody as a time to regroup and try for better the next time.