Kṛṣṇa describes the reward for the disciplined yogī. One whose mind is peaceful and whose mode of passion (‘Rajas’) has been stilled attains the highest perfection of transcendental happiness. They become ‘brahma-bhūtam’, or qualitatively one with the Supreme nature. When the ‘fever’ of passion and ambition dies down, the heart becomes ‘akalmaṣam’, free from the stains of past actions. This ‘Uttamam Sukham’ is the natural state of a soul that is no longer being agitated by desire. It is a joy that comes from being internally ‘clean’ and ‘quiet’. Kṛṣṇa is showing Arjuna that the peace he is searching for is only available when he stops being driven by the ‘rajasic’ energy of conflict and ego. By reaching this state of ‘Brahma-bhuta’, Arjuna will experience a happiness so intense and pure that the external world will lose its power to disturb him. True joy is the byproduct of internal stillness.