It means that a yogi should be free from dualities. The level of Nirvana means cessation of material activities.
Anything created, thought, done etc on the personal basis devoid of the interest of Hari falls under the category of the 3 modes of material nature [Goodness, Passion and Ignorance].
Buddhism limits itself with the level of Nirguna, but above that level comes Bhakti, which is the last stage...
That is working for Hari, since Hari is Brahman, obviously, we'll start working for all the living entities, regardless of his\her maili chaadar [garment].
Concerning leaving Goodness is quite an esoteric topic, Arjuna spoke a lot, but Krishna said "what you are saying stands with of lots of morality in appearance but is nothing in substance."
What we might think is Good from our personal perception might not be so in a universal or more global terms.
That's why what has been planned by the Perfect, i.e, Krishna is always perfect, and his plans are free from the material modes of nature, thus abiding by his plans is known as Bhakti.
Following his plans is the Real Good.
Krishna also said in the Gita, whether you choose to raise your arms or not, does not really matter, when I got up I already killed them; if not you, then someone else will do the Job.
But to be Krishna's servant is a very difficult and another story.
He knows to whom he should relate the Gita.