The Collaborative International Dictionary of English v.0.48:

Self-command \Self`-com*mand"\, n.
   Control over one's own feelings, temper, etc.; self-control.
   [1913 Webster]

WordNet (r) 3.0 (2006):

self-command
    n 1: the trait of resolutely controlling your own behavior [syn:
         self-control, self-possession, possession,
         willpower, will power, self-command, self-will]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "self-command":
   aplomb, assurance, balance, composure, confidence, constraint,
   control, discipline, equability, equanimity, equilibrium,
   independence, level head, levelheadedness, poise, possession,
   presence of mind, restraint, self-assurance, self-confidence,
   self-conquest, self-containment, self-control, self-denial,
   self-discipline, self-government, self-mastery, self-possession,
   self-restraint, uncommunicativeness, well-regulated mind,
   willpower