The 25-year-old actress revealed she wasn`t happy with her career and felt she had missed out on a normal life but the chance to work with fellow British star Carey Mulligan on `Never Let Me Go` changed her mind.
She told Britain`s Vogue magazine: "I didn`t know if I was going to go back to acting at all. I think for a long time I thought I wouldn`t. I think I intended not to work again."
"Carey`s a very good friend of mine and I felt if I was to start making films again, she was someone who would watch my back."
Keira - who is in a relationship with actor Rupert Friend - explained she considered quitting acting is because she had become disillusioned with her privileged life but also because she was desperate to go on vacation.
She said: "I wasn`t enjoying what I was doing and I felt terribly guilty about that.
"I remember hating the idea that I was in a privileged position and couldn`t see the point of any of it.
"I had worked solidly since I was 16, till 22, and I had not been on holiday in all of that time."