In an interview about his book Extreme Medicine, Dr. Kevin Fong discusses how life in space is far from cozy:
When you see space men and women on television you get this impression that it’s sort of like a slightly more fun version of a super long-haul passenger flight that, you know, it’s a quite comfortable experience and they’re just floating around there having quite a lot of fun while engaging in quite a serious task. But when you get down into it, you realize that these expeditions are true expeditions — expeditions really in the same sense that walking into the deserts or climbing our highest mountains, or exploring our polar regions are — that you go into this environment and you learn the same lessons from it that you learn everywhere else in exploration, and that is that we can exist there, but not forever and not without penalty.
[Due to lack of gravity] they experience [the] wasting of their bones, wasting of their muscles, deconditioning of their heart … They have problems with their hand-eye coordination. It seems that the apparatus in your inner ear that detects acceleration — that helps you with your day-to-day hand-eye coordination — also gets pretty messed up up there, and so they have problems tracking moving objects with their eyes, and … they feel pretty sick. In fact, most rookie astronauts feel sick or are sick in the first 24-48 hours of flight. So when you see them up there on-camera, waving and smiling at you, you have to know that underneath that is a lot of discomfort for lots of them.
The Dish 