Easy to say if that is what you experienced as an airline pilot but there are parrallells with instructing too; such as: unsociable hours (ie; every weekend!), the weather disrupting our schedules, flying schools constantly going bust, selling up or downsizing fleets... But despite that we still love it.
Talking purely about the job in general and not the instruction side itself particularly - what I like most about my current employment status is that there are no little Hitlers controlling my working day! I pitch up, A-check the aeroplanes amongst the glorious english countryside, teach my students how to fly properly (my favourite part), occassionally have to indulge in some boring paperwork (but not very often!) and then I am home at the end of each day within 5 minutes. The people I work with are decent people who enjoy the job for the same reasons as myself - there's almost an unspoken rule that we'll enjoy each working day because we all understand the passion! As you say, the airlines aren't that understanding.
Pitts or Boeing? Gotta be Pitts!!
VFE.