The businesswoman, who rarely even finds time for a holiday, said she thought her career would be in jeopardy otherwise.
But in an interview with Hello! magazine she admits she made a mistake not to spend more time bonding with her daughter Sophia, now 14.
Brady, 41, said: "It was a mistake and most people would look on it with shock, as they should. When you're young and in a career, you don't think it will last a lifetime.
"You think it will slip through your fingers if you take time out."
The West Ham vice-chairwoman, who recently became a member of Lord Sugar's team for BBC1 series The Apprentice, was interviewed as she enjoyed only her third holiday in 15 years.
Brady also has a son Paolo, 11, with her husband of 15 years, Burton Albion manager Paul Peschisolido.