The problem with science, from the viewpoint of a scientist, is that thing invariably go wrong. If it's Biology, it dies. If it's Chemistry, it explodes (or goes 'phut' if you meant it to explode) and if it's Physics is just doesn't work.
Having spent the afternoon battling a recalcitrant piece of vacuum kit - the pumps are sucking as hard as ever, but there's a huge leak somewhere in the main sample chamber - I really needed a break. But although my kit isn't exactly designed for ease of maintenence, at least I can get to it when it breaks down, rather than have to sit there and watch it doing nothing 600km overhead. Hubble isn't due another servicing visit until September 2008. The replacement, the James Webb Telescope, isn't going to be ready until the middle of the next decade.