The ancient Greeks may not have been terribly advanced in the practice of medicine, but at least Hippocrates had a good idea of the principles that a practitioner of medicine should have.
"With purity and holiness I will pass my life and practice my art," wrote Hippocrates in his oath. It called for devotion to the craft of medicine above all else. It was perhaps his greatest gift to the medical profession. The techniques and theories of medicine may have improved with the passage of 2,500 years, but the principle of disinterested service to others remains a critical part of medicine. That principle carries over into other endeavors, for a true professional lives his life with purity and practices his craft in a way that serves others.
Likewise for Hippocrates' observation that "timidity betrays a want of powers, and audacity a lack of skill. They are, indeed, two things, knowledge and opinion, of which the one makes its possessor really to know, the other to be ignorant."
Knowledge is the most important thing. It can overcome everything else. It's the only thing that matters.