Ziglar, who had been suffering from pneumonia, died at a hospital in the Dallas suburb of Plano, said his personal assistant, Jay Hellwig.With an aim at helping people achieve success in their careers and personal lives, in addition to a focus on Christianity, Ziglar was a prolific speaker who appeared at events alongside world leaders including several U.S. presidents and former British Prime Minister Margaret Thatcher."Mr. Ziglar was the same guy behind the closed doors as he was preparing for his presentations to thousands of people that he was when we were sitting at the kitchen table and he was reading the newspaper," Hellwig said.Prestonwood Baptist Church Pastor Jack Graham, Ziglar's friend and pastor, said Ziglar "truly was filled with faith.""He was positive. He was hopeful. You just never heard negativity from Zig Ziglar," Graham said. "It wasn't just something he did on a platform. This was who he was. This is how he lived his life. And he helped so many people.""He was a leader of leaders and a mentor of mentors and all that you can say," he added.Ziglar started his fulltime career in motivational speaking when he was in his 40s. His first book was "See You at the Top."Hellwig said Ziglar "accepted Jesus Christ as his savior" at the age of 45 and "ever since, that day is what he said was the turning point of his life.""He also had the uncanny ability to make everyone he ran into feel like they were his friend," Hellwig said.Ziglar was a World War II veteran who grew up in Yazoo City, Miss., and then went to work in sales for a series of companies, where his interest in motivational speaking grew, according to his Plano-based company's website. Hellwig said Ziglar moved to Dallas in the late 1960s.Ziglar's company, which features more than a dozen speakers advocating the "Ziglar Way," offers motivation and performance training.His book, "Confessions of a Grieving Christian," was written after the 1995 death of his oldest daughter, Suzan Ziglar Witmeyer, at the age of 46.After a 2007 fall down a flight of stairs left him with a brain injury, Ziglar, along with another daughter, Julie Ziglar Norman, wrote "Embrace the Struggle," a book that described how his life changed after the injury.In addition to his daughter, Ziglar is survived by his wife Jean, with whom he celebrated 66 years of marriage on Monday; his son, Tom Ziglar; and daughter Cindy Ziglar Oates.A memorial service is set for Saturday at Prestonwood Baptist Church.