For the Sufi, therefore, breath is a key to concentration. The Sufi, so to speak, puts his thoughts under the cover of the breath. This expression of Rumi's I would interpret as meaning that the Sufi lays his beloved ideal in the swing of the breath. I remember my murshid's saying that every breath one inhales conscious of the Divine Beloved is the only gain there is, and every breath inhaled without this consciousness, the only loss.