Non-attachment is the sign of mastery of one who is not clinging to what is seen or heard.
There should be only one attachment and that is attachment to the Self within. The difficulty is that we are either not aware of that True Presence (the Self within) because of our incessant inner chatter and false identification and captivation with the ephemeral (like a deer in the spotlight) or we have glimpses of that Self within as either darshan (Self revelation) or Intuition (a soft whisper from an eternal source that is not mind chatter. As Parahamsa Yogananda used to say: Prayer is us (ego) talking to God (the Self) and Intuition is God (the Self) talking to us (the ego)) but we are unable to maintain that awareness. So we need to develop discrimination (Viveka) - make distinction between the ephemeral, our cravings for objects, the illusions created in the imagination and machination of the mind veiling the pure consciousness, and the true I AM THAT I AM, the Pure Consciousness, the Self. That will lead to detachment, to become non-attached to any phenomena generated by the mind. When we become settled in the state of non-attachment, we develop calmness, inner stability and a steadfast mind (Stithi Pragya). We develop true inner happiness not defined by any outer symbols of wealth, status or possession. We are no longer pavlovian in our approach or reaction to life. External objects no longer create an automatic stimulus and an instant reaction in our mind—we are now able to create distance in our awareness (calling into operation the Witness Consciousness) and respond (or not respond) from choice (discrimination—Viveka) versus conditioning. Through mastery of our mind, no-one and no-thing can own us. We become fearless. And only in the fearless state can we touch and be touched by eternity and immortality (the Self) for everything else will come to pass (including all the things that we normally identify ourselves as and with) save the Self.