Krishna offers one of the Gita's most compact and striking definitions. What is yoga? It is the severing of the bond between the self and sorrow. When the mind stops connecting with suffering — stops identifying with it, stops clinging to it — that disconnection itself is yoga. Nothing more complicated than that.
And how should it be practised? With nishchaya — firm resolve — and with an anirvinna chetasa, a mind that does not tire or grow discouraged. The practice will be interrupted. The mind will wander. Progress will feel slow. Krishna acknowledges all of this implicitly by insisting: do not quit.
A child learning to ride a bicycle falls many times. Each fall is not failure — it is part of the learning. The child who gets back on every time eventually rides without thinking. Krishna's instruction here carries that same spirit: keep going, without weariness, without giving up.