At least a few of major components. Being a hero is difficult enough, but there's no reason to look for perfection.

The willingness to adapt.
Various degrees of observational skills.
Tenacity.
Patience.
An understanding of one's limits.
Courage.

Those are a few, but they're some of the most important qualities to me. People want to be heroes for whatever reason, but universally it's to help others who need it. It would be easier if you asked me what I don't want in a student.