Mothers have been exhausted since the beginning of time, but some difficulties are specific to the millennial generation.There was dog urine on the carpet, vomit on her blouse and a queasy 7-year-old to look after, but Dr. Whitney Casares had just a few spare moments to clean up and change so she could resume the keynote presentation she had been giving when the school nurse called.Dr. Casares, 42, a pediatrician in Portland, Ore., tried to clean up both messes and race back to her computer. “But I was completely unnerved and underperformed,” she said. “When my husband” — who hadn’t picked up when the school called — “and younger daughter came home a few hours later, the first words out of their mouths were ‘Didn’t you get anything for dinner?’ and ‘Why does it smell so bad in here?’”In that moment, said Dr. Casares, the author of “Doing It All: Stop Over-Functioning and Become the Mom and Person You’re Meant to Be,” she related to a Taylor Swift lyric: “I did all the extra credit, then got graded on a curve.”It has always been exhausting to be a mother, but each generation has had its particular pressures and ways of coping. Boomer moms didn’t expect motherhood to be anything but difficult, though the lack of social awareness around anxiety and depression meant most would never openly discuss it. Generation X moms had to prove that they could do everything men could do — and then come home and work a second shift. Some Gen Xers were children of divorce, manifested an ironic detachment from their troubles and were prescribed Prozac to deal.And then came millennial moms, the women raised on “You go, girl!” in the 1980s and ’90s and who today are in their 30s and early 40s. On average, they enrolled in college in higher numbers than men, married later and delayed having children, sometimes to prioritize careers and other times because — with student debt and less wealth than previous generations — it felt impossible not to.Still, it seemed like some things had worked out in their favor. Perhaps they could juggle work and motherhood more successfully. Maybe their male partners, if they had them, would be more attuned to gender imbalances at home.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More