Man's own natural duty.........

    "Now you shall hear how a man may become perfect, if he
devotes himself to the work which is natural to him.  A man
will reach perfection if he does his duty as an act of worship
to the Lord, who is the source of the universe, prompting all
action, everywhere present.
     "A man's own natural duty, even if it seems imperfectly
done, is better than work not naturally his own even if it is
well performed.  When a man acts according to the law of
his nature, he cannot be sinning.  Therefore, no one should
give up his natural work, even though he does it imperfectly.
For all action is involved in imperfection, like fire in smoke.
     "When a man has achieved non-attachment, self-
mastery and freedom from desire through renunciation, he
reaches union with Brahman, who is beyond all actions."

-from Chapter XVIII
The Song of God: Bhagavad-Gita