। ॥ ३११ ॥
In plain words
Once you have overpowered this enemy, the ego, never give it an opening again by dwelling on the objects of the senses. That alone is enough to bring it roaring back - the way a little water can revive a citron tree that was nearly dead.
Close to the Sanskrit
Having subdued the enemy that is the ego, no opportunity should ever be given to it through dwelling on sense-objects; that alone is the cause of its revival, like water for an almost-withered citron tree.