Does the novel have to deepen the psychology of its heroes? Certainly the modern novel does, but the ancient legends did not do the same. Oedipus' psychology was deduced by Aeschylus or Freud, but the character is simply there, fixed in a pure and terribly disquieting state.
If you always put limit on everything you do, physical or anything else. It will spread into your work and into your life. There are no limits. There are only plateaus, and you must not stay there, you must go beyond them.