Cumberbatch explains that playing a drug addict with frequent mood swings is challenging. He says, “Playing it was exhausting. Although, to put it in perspective, not as exhausting as actually living that life. I’m wary of saying, ‘Yes, it was so trying,’ because all the best roles are.”
While Cumberbatch has spent a lot of time with some of his characters — such as Sherlock Holmes and Doctor Strange — he admits that when a day’s shoot is over he lets go of the character on set. He says, “Hell, yeah. Can you imagine taking that beast home with you?”
(via)