Just like when you find yourself dancing the night away at a concert or club.... or jogging miles past what you thought you could do and time just feels translucent... it's a steady rhythm that carries you. Like in your practice your breath or in your meditation your heart beat or breath that sings a rhythm that begs for the universe to play a melody to.
You feel this in your postures as you sync up your breath to a steady rhythm the movements and details of the posture plays a melody over it. If you settle to hear or feel the whole posture you notice each one has its own song in your wind instrument body or vessel. Your vessel for goodness, for light and for song!
So when you feel like you have lost your momentum come back to the rhythm which invites the dance of the universe to enrich and re-charge you.