When Should You Quit Your Job?
is a load of crap. The real statement should read "You do what you have to do in your chosen field, until you get to do what you want to do in your chosen field!". The only problem is that in life you can take on dependencies (family members who rely on your health care and/or constant paycheck) as well as not focusing the part about your chosen field.
I went INSANE doing tech support in a very corporate business environment in the hopes that I could move up to programming. From there I hoped to fill out my programming resume enough to switch to a company that did computer games. I never had enough time to really concentrate on programming and every time I sat in front of a computer I would hear myself asking, "ok, I need you to check and see if it is plugged in...". I have since quit that job and I am moving to another city in order to get on with a game company that is growing. I have no regrets except for the amount of time I put in doing a job that was actively devouring my soul...
So, if you aren't in the specific field you want to be, try and line up a job that IS in your chosen field first. However, don't let 'em devour too much of your soul before you split!!!