The actress left the BBC soap as Peggy Mitchell in September 2010, after first appearing in 1991.
She explained that she decided to leave the soap as she had begun "taking it home" too often, making home life difficult for her husband Scott Mitchell.
"I am steady, I know the business – I have been in it 63 years. I enjoy it, I like the public very much," she told The Mirror.
"I never take it home with me. Then one day my husband sat me down and he said, 'You know, Barbara, you are bringing it through the front door. Everything is Peggy this, EastEnders that. You are not switching off at all'.
"He said we didn't go anywhere, we didn't go to the movies or the theatre. So when they gave me that Saturday that was the thing that did it.
"It meant come Sunday I was learning my lines again. You hit an age when you have to study that bit harder – unless you are June Brown who, at 84, can pick it up and learn it in a second. But that did it."
Windsor stated that she didn't want her soap role to ruin her marriage, and that she is happy that she made the right decision.
"I don't want to kill what we have. He is much younger than me and it's not fair to him. I am very lucky, we have been together for over 20 years now and I thought, 'That's it'.
"That's when I decided to go. Hard it was, but I have been really happy since I left and we have had a great life. And now I can get away when we want.
"Me and Scott have had a lot more quality time together and we have had more holidays. When I got a holiday on EastEnders I would be taking a script with me. I couldn't relax and leave it behind."
She added: "I am not like my image, I take my work so seriously. Everyone thinks I just bounce in but I study and everything has to be just right.
"I check all my props, everything. Acting is something I love. I have done it since I was 13 but it had completely taken over my life absolutely."
Barbara Windsor also revealed that she had a secret friendship with Amy Winehouse.