The actress is on the cover of this week's People magazine, in which she talks about the disease and how she's coping.
The single mom of 8-year-old Arthur said longtime friends have rallied around her, including her "Cruel Intentions" costar Sarah Michelle Gellar and actress Jaime King.
"It's the strangest thing that the time that could be the most stressful, I am feeling the most joy," Blair told the publication. "I think it's because I've learned more than ever that there are people that support me, that love me. I've seen people dedicate their time to help me."
Blair, 47, went public last October with her diagnosis of multiple sclerosis, which affects the central nervous system. It is an autoimmune disease in which the immune system attacks its own healthy cells. Symptoms include blurred vision, and difficulty with coordination and balance.
The disease can be debilitating. Blair said Gellar started a meal train in which other stars provide meals for Blair and her son.
"I get weekend meal packs like I've never feasted on before from Reese Witherspoon, from Constance Zimmer and so many people I don't even know through Sarah," Blair said. "[My friends] have stood up in ways I never would have been comfortable with before."
She also said it's important for her son "to see me interacting with people and to see mom laughing with them."
The youngster has witnessed the toll the disease has taken on Blair's body. She uses a cane, has fallen down the stairs, and rushes to the bathroom when she feels sick.
But she said Arthur has a positive attitude.
"He says, 'Mommy's not sick. Mommy's brave,' " Blair said.
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