Krishna explains about Swa-dharmam (own nature) (2.31-2.37) and advises Arjun that as a Kshatriya he should not hesitate to fight(2.31) as it is his Swa-dharmam .
Krishna commences the Gita with 'that' which is eternal, unmanifested and pervades all. It is termed as atma for easy understanding. Then he talks about Swa-dharmam , which is one step before 'that' and subsequently comes to Karma .
The journey to realise the inner self can be divided into three stages. The first stage is our present condition, the second is realising Swa-dharmam and finally, reaching the inner self. In reality, our present condition is a combination of our Swa-dharmam , experiences, knowledge, memories and assumptions gathered by our wavering mind. Swa-dharmam gets uncovered slowly when we free ourselves from our mental baggage.
Kshatriya is the combination of ' Kshat ' meaning 'hurt' and ' trayate ' meaning 'to give protection'. Kshatriya is he who gives protection from hurt.
The best example is of a mother who shields the baby in the womb and protects the children till they are on their own. So she is the first Kshatriya we come across in our lives. She may be untrained and might not be experienced in childcare but it comes naturally to her. This trait is a glimpse of Swa-dharmam .
Once a rose was smitten by the majestic lotus flower and started nurturing the desire to be a lotus. But there is no way that a rose can become a lotus. The rose wanted to be different from what it is capable of and we have similar tendencies to try to be different from what we are, resulting in the despondency of the kind faced by Arjun. The rose can change its colour, size and shape, but will still remain a rose which is its Swa-dharmam.
Source - Daily World