"Boxes are for shoes, not people" is a simpler way of saying that as humans it is a miserable way to live when we conform and shape ourselves to fit into boxes (labels) others have created for us.
It is rather liberating to break away from that knowing that we do not need to maintain a structure or shape to be our most authentic self and that it is in our nature to blossom and evolve away from societal constraints.
Love,
Emmages