The Carry On and EastEnders actress, who made a rare public appearance on TV on Thursday morning wishing viewers a "happy Christmas", was diagnosed with Alzheimer's disease in 2014.
Husband Scott Mitchell said it feels like "a body blow" when his 82-year-old wife does not recognise him.
And he said the actress, best known as pub landlady Peggy Mitchell in EastEnders, is upset with herself when she realises what has happened.
"It hits her at different times," Mitchell told Good Morning Britain.
"Most of the time she knows me," he said, but added: "She can just look at me, straight in the eye, and say 'Do you know where my husband Scott is?'
"They're really tough things. It doesn't matter how used to it you get in a way.
"Each time it happens it's like a body blow.
"Then she realises it and then she's a bit upset with herself that it's happened.
"So there is that sense of isolation for the person as well. They also sense that life is going on and they're not a part of it like they used to be."
He told the ITV show, which broadcast a festive message from Dame Barbara, Mr Mitchell and the Alzheimer's Society: "Obviously the confusion is very unsettling for her."
But he said: "She's still got that lovely sense of fun within her. She still loves to sit there and giggle. I make her laugh, she makes me laugh."
His comments came after Dame Barbara delivered a letter, earlier this year, to Downing Street to plead for better care for fellow sufferers.
Mr Mitchell said he experiences "pangs of guilt" if he goes out without his wife and leaves her with carers, and I find "myself joining in, laughing and joking".
He said: "We've had some really consistent friends and family who have been there from the moment they knew about it.
"But I do understand also people have busy lives and sometimes feel a bit awkward.
"People ... don't know what to expect so they don't know what to say either.
"I do understand that."
Mitchell, who married the actress in 2000, spoke as Good Morning Britain announced the Dame Barbara Windsor Award for its One Million Minutes Awards.
"Barbara takes great comfort knowing that, although her own illness can be difficult at times, the fact we have brought awareness and can help others going forward is a wonderful thing and something she is very proud of," he said.