Half of all astronauts feel space sick because the balance system in the ears is not giving the brain signals of up and down any more. Fluids in the body also change. On Earth we are used to feeling gravity which pulls body fluids down towards our feet. When weightless this does not happen and more fluids than normal accumulate in the upper body and head. It takes two or three days before the body excretes this extra fluid as urine.
Team work is much more important now than it was in the early days of space travel.
To work well as a team with the other astronauts in your crew, you really have to know them well. On Shuttle missions, which are short, arguments are not so much as a problem, but for long Mir missions they can create difficulties. Russians have always put a strong emphasis on psychology and have carefully selected their crews. They do have their ups and downs but no severe conflicts have been reported. We had a guitar, a small keyboard, books, magazines and a video player, but mostly if we had any spare time we just looked out of the window.