Bg 3.19

tasmād asakta satata
k
ārya karma samācara
asakto hy
ācaran karma
param
āpnoti pūrua

Word for word: 

tasmāt — therefore; asakta — without attachment; satatam — constantly; kāryam — as duty; karma — work; samācara — perform; asakta — unattached; hi — certainly; ācaran — performing; karma — work; param — the Supreme; āpnoti — achieves; pūrua — a man.

Translation: 

Therefore, without being attached to the fruits of activities, one should act as a matter of duty, for by working without attachment one attains the Supreme.

Tasmād, therefore; why therefore? As in previous verse it is said it makes no difference to detached person to do duty or not do duty therefor asakta satata, therefore Arjuna while staying always detached kārya karma samācara, do your Karya do your prescribed duty, what will happen by that?

asakto hy ācaran karma, by performing work with detachment asakta, param āpnoti pūrua, you will attain Supreme Lord.

So in this way what Arjuna is told is to do your duty.

So Krishna is telling Arjuna over here yes, if you think that you are so self-satisfied that you don’t need a kingdom, you don’t need to be with your family, you can just go to forest and be satisfied there, fine then it makes no difference to you whether you are in forest or whether you are in city.

So Krishna is exactly turning around the same argument, the same point that I am so transcendental that I don’t need to do any duty so yes if you are so transcendental then doing duty also makes no difference to you.

So frustration in material life is not sufficient for spiritual life. It has to be positive attraction to spiritual life. And positive attraction is tested and demonstrated by sustained commitment, tested means for myself it is a test, today I may feel frustrated so I wanted to switch to spiritual life but even if in good time this desire is there then it is a test for me and demonstration for others. If that is there then one can renounce the material life and focus on spiritual life.

But if someone says I am so transcendental that I don’t care for my studies then well if you are so transcendental then whether you study or not makes no difference then study and set example for others.

So after that Krishna gives example to Arjuna, He gives him example of Janaka, His own example and then reiterated to Arjuna again that he should act.

But here He is giving general principle, therefor always be detached but kārya karma samācara do your work

asakto hy ācaran karma so if you will act in detachment then what will happen here Krishna for the first time Krishna is talking about param āpnoti pūrua you will attain the Supreme Destination, first time means He is using Param and referring to Himself, it  is not a direct reference, who is Supreme. Supreme is Krishna, Krishna is not using Mam over here but still param āpnoti pūrua, so one will attain the Supreme so Krishna is saying that just by doing one’s duty one can attain the Supreme and how one should do His duty by detachment,

But Arjuna is thinking but I have seen most people who wants liberation renounces the world so Krishna says no-no there are examples who remain in the world and they will also attain liberation.