It is necessary for the swimmers and divers to know the secrets of ocean in depth to protect themselves.
Similarly to live in this world, we have to know ourselves and the world around us.
Lord Krishna is giving out this Bhrama vidya not for sanyasis but sansaris who struggle day today to keep their balance of mind.
In this verse – Krishna tells Arjuna – do not take the burden of your actions as you are not the doer. You have no control over the world mind. So if you cultivate the virtues I have mentioned, you will conserve energy to fight the battles within you.
Practice the yoga of non-separation, which means your graceful inner self is always attacked by the wild imagination of ego centric mind. Unsteady mind creates doubts and you will sell your integrity and self respect for instant gratification.
Check this page for profound and easy-to-understand commentary of the Bhagavad Gita by Ms Vasantha Vaikunth