From an essay by the programming genius, painter, and start up maven, Paul Graham. By college he was beginning to question the work = pain formula that was received wisdom as a child.
The definition of work was now to make some original contribution to the world, and in the process not to starve. But after the habit of so many years my idea of work still included a large component of pain. Work still seemed to require discipline, because only hard problems yielded grand results, and hard problems couldn’t literally be fun. Surely one had to force oneself to work on them.
If you think something’s supposed to hurt, you’re less likely to notice if you’re doing it wrong. That about sums up my experience of graduate school.
Entire essay, How to Do What You Love, is pretty thought provoking.