A thought or emotion can feel like it's really something solid, but a minute later it's gone, nothing.  An image from Buddhist teaching is that all phenomena are like a line drawn in water.  Where is it?  In allowing the perceived solidity of a perceived something to breathe and shift, there is suddenly space for anything.  It has to do with resting and letting go, but not in a passive way, which is where I feel a strong parallel to the experience of yield in BMC, and also to cellular breathing. Letting go into complete presence.  Sometimes called bare attention, being with things as they are to us, without  emphasizing the stories we make of what we perceive. 
-- Kim Wishart June 2010 from writing, nothing<--->something