what did it meant when Mandela said "a Twilight existence of secrecy and rebellion"..??

Dear Student,

Mandela believed that a man had two obligations, one towards his family and the other towards his country.  He said that in South Africa, a man who tried to fulfill his obligation towards his country was forced to spend his life in prison away from his family. It was then that his life was refereed to be of twilight existence where he would not even know whether it was day or night. It was a life in isolation and secrecy. Thus, Mandela referred to life in prison as 'a twilight existence of secrecy and rebellion'.

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