Translation: One whose happiness is within, who is active within, who rejoices within and is illumined within, is actually the perfect mystic. He is liberated in the Supreme, and ultimately he attains the Supreme.
Purport: Unless one is able to relish happiness from within, how can one retire from the external engagements meant for deriving superficial happiness? A liberated person enjoys happiness by factual experience. He can, therefore, sit silently at any place and enjoy the activities of life from within. Such a liberated person no longer desires external material happiness. This state is called brahma-bhuta, attaining which one is assured of going back to Godhead, back to home.
"Krsna is within you. He is sitting within your heart as a friend, not as an enemy. Krsna is always your friend. Suhrdam sarva-bhutanam [Bhagavad gita 5.29]. You are searching out friends to talk with, to joke with, to love. Krsna is sitting there for that purpose. If you love Krsna, if you make friendship with Krsna, if you love Krsna, then your life will be successful. You haven't got to search out any other friend. The friend is already there. Either you are a boy or a girl, you will find a nice friend within yourself."
Lecture -- New Vrindaban, June 7, 1969