Crews on long missions do increasing amounts of exercise as the time to return home draws near otherwise their muscles that haven't had to do much over many months wouldn't be able to cope with the sudden gravity. Mentally, life on Mir can be quite tiring. Mir crews can talk to and se via TV, their families once a week and mail, newspapers and personal items are sent up every 2-3 months. Day to day living in space is also quite tricky to get used to. So many of the things we take for granted on the Earth are difficult to do or get hold of in space.
Water is a problem.
It is, however necessary to deliver extra water to space stations like Mir to top up the supply of recycled water. Future space stations are likely to have complete recycling systems whereby urine can also be recycled, which is technically not too difficult. People may not like the thoughts of it, but once the impurities are extracted, all that is left is plain water. Being ill can also be tricky. If the problem is really serious, Mir crews can usually head back home within a couple of days.