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So don't worry so much about how to use  had had  as a unit of grammar, they will come together naturally when you want to express the verb ' to have ' in the past perfect. Let's consider a different verb for a moment like  to want .
Languages may also have reflexive pronouns (and sometimes reciprocal pronouns) closely linked to the personal pronouns. English has the reflexive forms myself, yourself, himself, herself, itself, ourselves, yourselves, themselves (there is also oneself, from the indefinite pronoun one).