I was talking with a friend a few weeks ago about the sense of futility envloping much of what we do (scientific research). It's very hard to remind yourself every day that someone has to investigate what turn out to be dead ends, just to be sure they're dead ends and not something potentially useful. It can be very discouraging on a day-to-day level, though. I think before you get into research you picture it as a continuum of brilliant new discoveries, rather than the eternal culling of bad ideas, in the hopes of leaving only the good ones to flourish.