Mathemetician Herbert Robbins is best known for his book "What Is Mathematics?," but he is also a leading statistician. In an interview by Warren Page published in "Mathematical People: Profiles and Interviews" (Birkha user), he discusses the nature of his work:

Q: How do you feel about being a mathematician?

A: Let me answer your question this way. Most people acquire a certain expertise, and they work in fields where their expertise can be used. I don't have any expertise. If I were a Picasso, I could wake up in the morning and say: 'Well, I think I'll paint a Picasso today.' And by the end of the day I would have painted a real, genuine Picasso. Although it may not be one of my best, it would be another painting. Now if I get up in the morning and say, 'I think I'll do something in mathematical statistics,' at the end of the day I've got a wastebasket full of paper and nothing to show for it. And likewise the next day, and the next. I cannot do something by willing myself to do it, and what I finally produce is usually complete junk. I've probably wasted more paper than any mathematician in the world. I have no idea whether I'll ever do anything worth talking about for the rest of my life. I'm not even like a dentist who comes home and can tell his wife: 'Today I did three fillings and two root-canals, and I saved several people from serious tooth decay. Now let's have dinner.' What did I do today? I talked to a few people. I tried to think about something and it came to nothing. Finally, I found that I was just repeating what some other researcher had already done. The day's been a total loss.

Q: Doesn't this place a pretty severe burden on one's self-esteem and character?

A: Most mathematicians are unable to cope with this. I see so many who have stopped working, or are just repeating themselves and basking in former glory. There are so many ways this emotional deprivation can get to you -- the fact that you're just looking at the interior of your skull as though you were inside an egg, and there's no world except what you see inside. In most cases, there's no real contact with humanity, history or culture in general.