Fearlessness is extending ourselves beyond a limited view. The Heart Sutra, an essential teaching given by the Buddha, talks about going beyond. "Gone beyond" or gate in Sanskrit, is what we might call the basic no. The sutra says there is no eye, no ear, no sound, no smell—none of those things. When you experience egolessness, the solidity of your life and your perception falls apart. That could be very desolate or it could be very inspiring, in terms of shunyata, the Buddhist understanding of emptiness. Very simply, it is basic no. It is a real expression of fearlessness.
From "Overcoming Doubt" in Smile at Fear: Awakening the True Heart of Bravery, page 55.