In his new memoir “Promised Land,” former President Barack Obama opened up about the toll his presidency took on his marriage to his wife, Michelle Obama, while they were living in the White House.

In an excerpt from his book that was obtained by CNN, Obama admitted that he could “sense an undercurrent of tension” in his wife during their time as president and First Lady.

“Despite Michelle’s success and popularity, I continued to sense an undercurrent of tension in her, subtle but constant, like the faint thrum of a hidden machine,” Obama wrote. “It was as if, confined as we were within the walls of the White House, all her previous sources of frustration became more concentrated, more vivid, whether it was my round the clock absorption with work, or the way politics exposed our family to scrutiny and attacks, or the tendency of even friends and family members to treat her role as secondary in importance.”

He added that there were nights when “lying next to Michelle in the dark, I’d think about those days when everything between us felt lighter, when her smile was more constant and our love less encumbered, and my heart would suddenly tighten at the thought that those days might not return.”

“Promised Land” is set to be released on November 17. This comes after Michelle wrote in her own 2018 memoir “Becoming” about her and her husband’s struggles with infertility. She described the troubles they had with conceiving a child as “surprising as it was disappointing, saying that she even thought their conflicting schedules were to blame at one point.

“Our attempts at procreation took place not in service of important monthly hormonal markers but rather in concert with the Illinois legislative schedule. This, I figured, was one thing we could try to fix,” she wrote. “But our adjustments didn’t work, even with Barack flooring it up the interstate after a late vote so that he could hit my ovulation window and even after the Senate went into its summer recess and he was home and available full-time.”

The Obamas eventually worked through their struggles with infertility and went on to have two daughters, Malia and Sasha.