The actress, who played press secretary C.J. in the White House-based series, worked 18-hour days and rarely had time to socialise with pals.
And when the show eventually ended its seven-year run in 2006, Janney realised how much of life she had missed out on.
She tells the U.K.'s Sunday Express, "It was relentless. We did 18-hour days - and we were so happy to be where we were. But as the years went by, we started to be less happy. There are so many things I missed out on in my friends' lives. When it ended, I felt kind of adrift because I slept, ate and breathed West Wing. I really didn't have too much else to define who I was."