What the Bhagavad Gita says about duty
Arjuna's problem in chapter 1 is not that he does not know his duty. It is that he has two, both real, and they point in opposite directions. He is a soldier in a just cause and he is a member of a family he is being asked to destroy. The Gita never says one of those stopped counting.
That is why the book's treatment of duty is worth more than the usual summary of it. 2.47 is quoted everywhere: you have a claim on the action, never on its results. Less quoted is 18.48, which says every undertaking is wrapped in some fault as fire is wrapped in smoke. The trouble in your work is not evidence that you chose wrongly. It is evidence that you chose something.
And the ending refuses the tidy version. 18.66 tells Arjuna to let go of all duties and take shelter instead, which only means anything if the competing claims were genuine the whole way through.
The verses 14
2.31
And if you look at your own work in the world, you have no reason to waver.
2.32
Lucky are the warriors who get a fight like this one, Arjuna - arriving unasked, an open door.
2.33
But if you will not fight this rightful fight, then you throw away your own work and your good name, and you take on the fault instead.
2.38
Treat pleasure and pain as the same.
2.47
Your claim is on the action alone, never on its fruits.
3.8
Do the work that is yours to do.
3.19
So do the work that is there to be done, always, without holding on to it.
3.20
Janaka and others reached the goal by action alone.
3.35
Better your own work, done badly, than someone else's work done well.
18.7
Giving up work that is genuinely yours to do is not right.
18.9
When work that is genuinely yours is done simply because it is to be done, Arjuna, with attachment and fruit let go, that letting go is the clear kind.
18.45
A person reaches fulfilment by taking delight in the work that is his own.
18.47
Better your own work done imperfectly than someone else's work done well.
18.48
The work you were born to should not be given up even though it has faults in it, Arjuna.