My tuppence worth...
My heart was in it 100% up until last summer (note... long time before 9-11). I spent the summer hauling gliders, which was OK. Allowed me to put a load of valuable hours in my logbook, get some free instruction with good people and do some (excellent fun!) gliding.
However, for one reason or another, which I won't go into here, I think that the summer could have been better. Basically at towards the end of the summer I was already thinking about not flying professionally at all. To be honest, for me, it took a lot of the fun out of a potentially very fun persuit. Maybe I was doing something wrong, but I no longer felt challenged.
Then along came 9-11, and it really did make sense (at the time) to not fork out a load of money to do some training. So of course, I applied for other non-flying jobs. Amongst those, a career that I'd always thought about doing, but it always took second place to flying.
My application was successful, and now I've started the long route to fulfilling my other ambition. However if I can't pull this off (50% don't), then I'd look at flying again.