My research supervisor told me that my only mission is to turn in a good thesis at the end of two years. Okay, and do well in my courses. That's all he's asking for. =)
It helps that I actually enjoy looking for funding and thinking of useful projects, but if push comes to shove, I should focus on something I can write and finish than just on something that's well-funded.
I'm not even writing a Ph.D. dissertation, just a master's thesis. Master's theses are much shorter than Ph.D. dissertations. I can get away without inventing a whole new field, for example. =)
Thanks to Luis Fernandes for the tip!