The turning point is described here:
But there was no question that they were a couple and a team. In time, Michelle made the conscious decision that, in fact, she would be the one to adjust to the circumstances he created - and not vice versa.Michelle Obama made the decision that many women make. The situation is complicated by the fact that they both thought he could change the world in important ways. Still, in most of the cases that I know of, she is the one to make the adjustments to make the family work. There are a few cases that I know of of very high achieving women whose careers depended on husbands who made big career sacrifices. The Thatchers are the best case I can think of.
"This was the epiphany," she said. "What I figured out was that I was pushing to make Barack be something I wanted him to be for me. ... I was depending on him to make me happy. Except it didn't have anything to do with him. I needed support. I didn't necessarily need it from Barack."
Michelle decided to approach the problems in her marriage the way she would approach the problems she faced daily at work. "I had to change," she said. "So how do I stop being mad at him and start problem-solving, and cobble together the resources? I also had to admit that I needed space and I needed time. And the more time that I could get to myself, the less stress I felt."
What happens if one of them doesn't make the adjustment? I think in 99 cases out a 100, neither of them reaches the heights in public life that one of them might have reached. Most parents will judge this worth it. But I think that is a real choice that couples with the potential for stratospheric achievement have to make - one of them has to be the main family makers. And, in my estimate, in at least 8 couples out of 10, she will be the one who chooses to make the adjustment. Not forced. But chooses, all things considered.