Be strong, and quit yourselves like men.

-Bible (Old Testament)
Samuel 4:9.

I won't quit until I get run over by a truck, a producer or a critic.

-Lemmon,Jack (John Uhler)
  In Newsweek, 5 May.

Once you learn to quit, it becomes a habit.

-Lombardi,Vince(ntThomas)
Attributed. US  writer.  His  books,  such  as The  Call  of  the Wild  (1903)  and White  Fang  (1907),  reflect  his  experiences  as  a  sailor,  tramp, gold  miner  in  the  Klondike  and  alcoholic.  He  also  wrote  a futuristic political novel The Iron Heel (1907).

I don't believe that I ought to quit because I am not a quitter.

-Nixon, Richard M(ilhous)
  National T V broadcast after allegations that he was financing his vice-presidential candidacy from a secret fund, Sep.