I've been wondering these very things for the past few months.
I've put so much effort and time and money(!) into becoming a pilot, and I feel like getting out now just sums up to giving up. But then I ask myself, is it being practical (cutting losses), or is it giving up?
The flying has never been an issue.. it's just all the other parts of the job.. frequently working 14-15 hours a day and getting paid for 6.. getting jerked around constantly by the company, the realization that I am letting this abuse happen to me instead of taking control (and getting out of it).. the commuting.. god I hate commuting.. the reality that I may work hard at a regional for years but never advance (be it to a major, a fractional, etc.)
and, like some others have mentioned above.. I ask myself how I would feel a few years down the line.. especially when I see that my current coworkers had stuck it out and advanced in their airline careers... wondering what could have been for me, too.