This happened to me three months ago. Was with my gf for 3.5 years. We were both in the same graduate program and are working professionals with aspirations to pursue a PhD and make it in our fields. Anyway, like I always do, I started brainstorming out loud with her what to do after our MPA, whether to pursue a PhD now or later, so on and so forth. Simultaneously, I received a new job offer that differed in no way to my then-current job with regard to schedule, but at the same time I was attempting to keep my older job as a part-time gig because I would have been paid approximately 20-25 hours per week for what amounted to 5-10 hours of work from ANYWHERE, be it home or in the office, so I thought it naive to turn down extra income, especially since we both desperately need it.
Turns out she thought I wasn't thinking of our future, which is bogus because we always discussed moving in and marriage and were very much serious and in love with each other. She suggested that I would be too occupied for us and that I should take a break to determine whether the part time job would interfere with our time, which is counterintuitive because I would need to be actively dating her in order to see if I'd be able to make it work.
Anyway, after a week of glossing over most of what should have been evident at first, I didn't feel like going back. I don't know if it was her attempt to rustle some leaves to feel cared for or to see how far I would go for her, but I couldn't justify being with someone who couldn't handle the idea of being with someone who is busy with work and school. Worse yet, she wants to do the same things and naturally as adults seeking to move up the corporate ladder, we would be getting busier. But as of right then I was working 9-5 with some hours from home for the part time job and planning to pursue a PhD by 2018 at the latest, but because she freaked out now, I couldn't and didn't want to return because I knew I'd feel like I am walking on eggshells.
It sucks because I always encouraged her to be as proactive and successful as possible while maintaining I'd still be by her side, but I don't think she was able to express the same feelings without wanting to breakup because she needed more time or attention.
To your topic, OP, I mention all of this because for the first two months I was depressed and not doing too well, until I really came into my own and convinced myself, for better or worse, that if she couldn't handle me working a 9-5 and a few hours at a part time job, with the prospect of a PhD in the future, even though she was looking toward a PhD as well, then it wasn't meant to be. If she feels this way now, then it's only going to get worse in the future and I didn't want to try to make it work because I felt it would be futile anyway. It also didn't feel very fair to me.
Convince yourself that she is doing what's best for her. Channel that thought because it'll make you a little angry and possibly propel you to say, "Well, fuck it, if she can work on herself then so can I." You are your best friend. Improve yourself and work toward your goals. She is but a component to your life that is replaceable. You are the main hardware. Replace what doesn't work or eliminate it all together. Think of this as a stepping stone with regard to experience and freedom.