#diffidence__self-doubt__self-distrust  lack of self-confidence
  exclusion:  confidence
  supertype:  timidness__timidity__timorousness  fear of the unknown or unfamiliar and of making decisions
  subtype:  hesitance__hesitancy  a feeling of diffidence about doing something
  subtype:  unassertiveness__unassertivenes  diffidence about self promotion

No statement uses or specializes diffidence; click here to add one.