Are you creative? Flying a jet transport is demanding, but it isn't creative and I know a few who have gone that route and regretted not being able to stretch the creative side of their natures. Most demanding careers have a strongly creative element, especially in business.
The upside is that when you walk away from the aeroplane, the job's done. Until the next flight. Most demanding careers aren't like that - you live them (even if not actively engaged in them when not at work) 24/7. That can be stressful for some.