For the record, I've never been dead-set on grad school. Even now that I'm in grad school I'm not all that attached to it. However, a Master's degree has become a prerequesite for most permanent positions in my field, and since I'd like to be able to work without moving around all the time, I'm willing to jump through some hoops to get there.
I wound up applying during my senior year of college to two schools. School A rejected me (along with 90% of the other applicatns) but by the time that rejection rolled around I decided I didn't really want to go there anyway. I was done with major city living. The other school had rolling admissions and when I hadn't heard back by April, I started making other plans. I think that was for the better since I was a bit burned out with school. I applied for some summer jobs and landed one in my field. I made a promise to my significant other that I'd go where he was working in the fall and withdrew my application only to find out I would have been admitted. (I reapplied the next year and got in no problem).
I'm a grad student but I've still got a plan B (and C and D...). I'm willing to try new things. If something happens to screw me over in my program (i.e. if experiment fails and I can't complete my thesis) I'm not afraid to leave. I know I can learnand that there are many jobs which would make me happy. If grad school doesn't work out, or if I don't like my first couple jobs, who knows? I'd try being a baker. I'd try being a tutor. I'd be willing to volunteer overseas.
Life is about so much more than work and school. I'd regret it if I became so work-o-holic that I lost my relationship. I'd regret if I missed out on raising kids in a few years. I'd regret it if I didn't have chances to travel. However, I don't think I'd regret not spending enough time invested in my career.