As a grad student in math, i would say that determination still plays a important role. For me, there have often been periods where you lose motivation and dont see why you are doing what you are doing, and then sometimes there are moments of clarity. (someone aptly compared this to mountain climbing). I imagine this happens in lots of other fields,(music, to pick a random example) where there is a prequisite of learning lots of arbitary things before understanding/creativity happens. Determination, is what you might need to to go through these phases.