eloise rummaging - big hype, big letdown

So I'm thinking about leaving my PhD program. I'm in my 7th year and have drafted two pretty bad chapters of my dissertation. I haven't produced anything of note since last spring and keep blowing deadlines. I decided last spring that I didn't want an academic job (I'd like to go to library school instead); this was the end result of struggling for the three years since I took my qualifying exams to feel like I belonged in the profession. My funding is over after this year, so regardless of whether I continue to work on my dissertation or not, I need to find a job. The usual path for grad students in my situation is to teach three comp courses a semester; I found teaching two at once overwhelming and also have discovered I don't really enjoy teaching.

I don't like the person grad school has made me become. I don't read books much anymore because book remind me too much of the work I should be doing. I don't watch much TV because I feel guilty when I'm not pretending to work--even though I've been getting hardly any work done. I haven't knit in months for much the same reason. Oddly enough, socially, I am happier than I have ever been. The highlights of the last three years of my life have mostly been fandom-related--I've made a lot of really good friends via fandom and had a lot of experiences I would not have had otherwise. Trying new things via fandom has made me realize there's a life outside of academia and that I am probably not a person who is going to be defined by her job. There's a different world out there for me.

So why, given all of that, do I still feel compelled to hang on? I've invested a lot of time in my degree, for one thing; I'll be 30 this year and I've been in grad school since I was 22. For another: I'm afraid that quitting this--the biggest thing I've ever done--makes me a quitter. Logically, I know it doesn't; our lives are never defined by one choice--at least outside of fiction. But there's a part of me that wonders if I just want to run away because it's gotten too hard. How do I figure out the difference between "too hard and must persevere" and "too hard to go on"? I'm tired of turning this problem over in my head (probably as tired as everyone i know is of me talking about it...). Have not yet been struck by the magical beam of insight I've been hoping for, though.