This verse is the distilled essence of Karma Yoga. Krishna says: therefore — given everything I have told you — act without attachment. Do what needs to be done. Do it always. Do it steadily. And let go of the results.
The word 'param' at the end carries the promise. Through detached action, a person attains the Supreme — whether that means moksha, God-realization, or the highest peace. Unattached action is the bridge that connects ordinary daily life to the extraordinary. You do not need to leave the world. You only need to change how you hold it.