IMO, life as a researcher is similar to the life of an artiste (h/t @johnregehr). You have a vision to do something, and you receive patronage from folks who believe in you and your vision. The primary motivation to do this is because you ENJOY it.
@johnregehr The best motivations are always intrinsic. If you are too hung up on "solving the most important problem in the field", you will be miserable. If you do science just so you can get a Nobel or some other award, you will be miserable.
What makes a work "great" is often a function of what else is happening in the world. For example, deep learning wouldn't be possible without all the advances in systems. Did they predict it when they came up with deep learning? No.
You do work that you think is good, that you can be proud of. If you are lucky, sometimes that work becomes "great". But often, it has little to do with you, and a lot to do with luck.
