to leave one to himself

Himself \Him*self"\, pron.
   1. An emphasized form of the third person masculine pronoun;
      -- used as a subject usually with he; as, he himself will
      bear the blame; used alone in the predicate, either in the
      nominative or objective case; as, it is himself who saved
      himself.
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            But he himself returned from the quarries. --Judges
                                                  iii. 19.
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            David hid himself in the field.       --1 Sam. xx.
                                                  24.
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            The Lord himself shall give you a sign. --Is. vii.
                                                  14.
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            Who gave himself for us, that he might . . . purify
            unto himself a peculiar people.       --Titus ii.
                                                  14.
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            With shame remembers, while himself was one
            Of the same herd, himself the same had done.
                                                  --Denham.
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   Note: Himself was formerly used instead of itself. See Note
         under {Him}.
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               It comprehendeth in himself all good. --Chaucer.
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   2. One's true or real character; one's natural temper and
      disposition; the state of being in one's right or sane
      mind (after unconsciousness, passion, delirium, or
      abasement); as, the man has come to himself.
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   {By himself}, alone; unaccompanied; apart; sequestered; as,
      he sits or studies by himself.

   {To leave one to himself}, to withdraw from him; to let him
      take his own course. Himselve
      Himself