QUESTIONS ON OBSESSION

Some questions arose today during my shower immediately following practice. 

What is the difference between an asana practice and a Yoga practice? How to tell if they are one and the same, or if they've diverged?

Is it possible to have a healthy obsession? Maybe a healthy obsession eventually expiates the obsession. Can you be obsessed with not being obsessed? (Fundamentally non-fundamentalist.)

A hard realization appears to be: we are not guaranteed 'completion' of an asana (leg-behind-head/pelvis-femur genetics as prime example). Then what is left? 

Are the sequences still meaningful if some of the postures within them are not completed 'perfectly'?