I’ve been reading Madam Secretary: A Memoir by Madeleine Albright. Ms. Albright’s summary of her experience in a PhD program:
Getting my Ph.D. was the hardest work I have ever faced on my own. It took thirteen years. I began when Anne and Alice were barely out of their cribs. When I finished, they were in high school. In between they taunted me, saying they shouldn’t have to finish their homework if I couldn’t finish mine.