The four levels of competence:

  [ Unconscious Incompetence ]  -->  "You don't know what you don't know"
             ↓
  [ Conscious Incompetence ]    -->  "You know what you don't know"
             ↓
  [ Conscious Competence ]      -->  "You know, but you have to think about it"
             ↓
  [ Unconscious Competence ]    -->  "You know it so well, it's second nature"