Interesting talk by a well-spoken and insightful guy.   He talks about the demoralizing effect of seeing no effect from your work.  He describes his experiments designed to show how important a sense of meaning and progress is to continuing to do good work.

The good news: it takes little conscious planning, and little effort, to motivate good work.  The bad news: it takes far less consciousness or planning, and no effort whatsoever, to demotivate.

Twenty minutes, interestingly spent.