After defending my thesis and reflecting on my past years as a graduate student, I was thinking about some of the big differences between being a graduate student and being an undergrad. Most undergraduates seem to see graduate students as extremely dedicated, hard workers with no time for anything else than research. This is most often not the case at all. The big differences between undergrads and grad are social opportunities, uncertainty, motivation and independence.
As a graduate student, you are essentially a full time student your first year or two, taking a full load of classes. However, unlike an undergrad who typically always has a least one class outside of their major, the graduate students' classes are very focused on their field. This also means that they tend to have the same people in every class, not providing much opportunity to have a broad social base. The undergraduate typically, however, will have classes from at least a couple of different fields. This leads to a much larger social base I think. Undergraduates seem to always have way more friends from many more different areas.
Every finals week, I look at all of the undergrads stressing about their exams, and I think to myself that I am glad that time for me is over. However, graduate students working on Ph.D.'s, in particular, face perhaps a tougher issue - uncertainty. Once you finish classes and start research, you typically don't have classes anymore which means no exams and for the most part, no real deadlines. However, I have spent months working on things which have no guarantee of producing anything interesting. This huge uncertainty with graduate research leads to another big problem - motivation.
Most undergraduates are not completing their assignments the moment they get them or are always excited about their work, but the deadlines inherent with undergraduate classwork force them (at least in most cases) to at least do something in some kind of timely manner. The lack of deadlines in the research phase of graduate school means that, for the most part, whatever you get done, you have to set the timeline yourself. In many cases, the timeline is much, much longer than it could have been. Note that the lack of deadlines in graduate school is not an inherent problem with the advisor or the system. By definition, the research a graduate student does is supposed to be new and original. It is hard to put a deadline on doing something that is totally new and may or may not have a solution or be interesting.
The uncertainty and potential motivation issues with graduate school are largely due to independence. No longer do you have a well defined schedule of homework and exams. As a graduate student, you are mostly on your own. For the most part, no one will care if you don't really do much work for a week or even a month, although naturally, this depends on your research advisor. Some people thrive in this, but from my personal experience and conversations with other graduate students, this is a very tough place to be. I used to say that in physics, for example, our classes take us to about 1950, but we are expected to do 21st century research right after that. I can imagine this is very similar in other fields as well. We are essentially tossed in without a life preserver.
I can say that the average graduate student I talk to feels their work is mostly useless, their contributions to their field are minimal, and their confidence in their work is shaky. He or she spends a lot of time surfing the web instead of working, can recall many times where they did not do a single thing associated with research for days or even weeks, and often thinks about quitting their program. I have never met a graduate student who works as long or as hard as a typical undergraduate. The undergraduate, however, knows exactly what they need to do to graduate, where the typical graduate student has no idea. Being a graduate student is certainly not all bad. It's just very different from being an undergrad.