In her new memoir, Hillary Rodham Clinton pens a moving tribute to her late mother, Dorothy, writing that if she were still alive, she would be urging her to "never quit."

On Sunday, Vogue Magazine released an exclusive excerpt from Clinton's book, "Hard Choices," pegged to Mother's Day, in which the former secretary of state describes the impact her mother had on her life.

"Mom measured her own life by how much she was able to help us and serve others," Clinton writes. "I knew that if she was still with us, she would be urging us to do the same. Never rest on your laurels. Never quit. Never stop working to make the world a better place. That's our unfinished business."

Clinton's book, to be released June 10, comes as she is considering whether to seek the presidency again. She would be the overwhelming favorite for the 2016 Democratic nomination. Clinton has said that she is weighing whether she can have a greater impact on the world as president or through global charitable initiatives by her family's foundation.

In the excerpt, Clinton writes that she confided in her mother during the difficult months after her bruising loss to then-Sen. Barack Obama (Ill.) in the 2008 Democratic presidential primaries.

"I'd come home from a long day at the Senate or the State Department, slide in next to her at the small table in our breakfast nook, and let everything just pour out," she writes of her mother, who lived with her in Washington through the 2000s.

Clinton describes her mother's lonely and abusive childhood and writes that she became a "fiercely independent woman," helping her granddaughter, Chelsea, navigate the difficulties of growing up in the public eye.

Dorothy's health began to fail her during Clinton's tenure as secretary of state, and she had heart problems. She died in 2011.

"Mom was a fighter her entire life, but it was finally time to let go," Clinton writes. "I sat by her bedside and held her hand one last time. No one had a bigger influence on my life or did more to shape the person I became."