I recently heard this (true) story, and I have still not figured out whether it encourages or discourages me. Anyway, here it is. A Phd student colleague of mine heard this from his mentor (dissertation supervisor):

When I was a PhD student, I shared my academic struggles with my own mentor. I told him I was struggling to make any progress. My mentor asked me “Are you working hard?” I said,  “Yes. I work 10 hours a day in the day time and then another two at night.” My mentor said, “Then, you are making progress!”  And sure enough, within a few days I was able to make a huge breakthrough.