security blanket

security blanket
    n 1: anything that an adult person uses to reduce anxiety
    2: a blanket (or toy) that a child carries around in order to
       reduce anxiety
    

19 Moby Thesaurus words for "security blanket":
      aid, backing, carriage, carrying, maintenance, moral support,
      psychological support, reliance, subsidy, subvention, support,
      supportive relationship, supportive therapy, sustaining,
      sustainment, sustenance, sustentation, upholding, upkeep