"My friend, Special Olympian Eddie Barbanell, wrote me a beautiful note before I traveled to Athens that made me feel so good," she wrote on her blog before leaving for Greece, where she will attend the Special Olympics World Games.
"He said that he knew I was going through a rough time but he wanted me to know that I 'will never be left out.'"
Maria, who is a member of the International Board of Special Olympics, said it was poignant that Eddie had delivered the message.
"Special Olympians, and people with intellectual disabilities in general, have experienced the feeling of being left out over and over again," she wrote.
"This makes them wise teachers on this topic."
Maria, whose husband recently admitted fathering a child with a former household employee, added: "Thousands of people – family, friends, neighbors, colleagues and many people I've never met – have reached out to me recently with loving, uplifting, hopeful and kind messages."
"But he was the only one who wrote, 'You will never be left out'."
The 55-year-old, who will attend the sporting event's opening ceremony on Saturday also chronicled the atmosphere in Athens.
"There is an incredibly strong spirit of unity here," she said.
"My brother, Tim, talks often about launching a 'Dignity Revolution' throughout the world and you can definitely feel that in the air."
Maria's estranged husband is currently in Austria.