"Flow" would be the ultimate in student engagement.
As I listened to Cskiszentmihalyi talking about the poet & ice skaters feeling of flow I tried to relate to instances that students may get to experience and feel that feeling of 'flow'. One is texting - where the students no longer think about where each letter is on their cellphones but think in words (sequences of letters) - much the same skill as me touch typing this message (I am not thinking about my fingers but in sentences). Driving would be another instance of "everyday" flow - the mathematical calculations we are undertaking simply turning a corner are complicated - but are done on automatic pilot. Both are skills which took time to achieve - but they happened. Perhaps these examples could be used when encouraging students - to keep on going/trying - in order to reach that experience of 'flow'.
I also liked Cskiszentmihalyi's 7 point table of How it feels to be in Flow: Points (3) knowing what is to be done - knowing how well we are going; (4) knowing it is doable; knowing our skills are adequate to the task are things that as teachers we could assist with to help students gain that sense of flow. eg:
Knowing what is to be done - could equate to giving good student instructions;
knowing how well we are going - to effective feedback.
Knowing it is doable - teachers giving students tasks they know are attainable - with exemplars, scaffolding and support.
Knowing our skills are adquate to the task - having students do formative tasks that prove to both students and teacher that the skills are there; and if not fixing the gaps.