I did a Science PGCE 2 years ago now. I did have a live outside the course- in terms of being able to socialise with friends etc. People do manage to keep up sporting commitments during the PGCE, but it does depend how much you want to train. I'm pretty sure most people who started the course in a relationship stayed in one throughout.
It is a tough year- my NQT was much easier. There's a lot to juggle, you can end up with a long commute, and there's a lot of "stuff" you have to do for the PGCE which takes up a lot of time and feels a bit pointless. But obviously most people get through the year (although drop out rates are high) so it can't be that bad!
I think a year out to work is always good before doing a PGCE though- it tends to be those coming to it straight from uni who find it a huge culture shock.
If you share your specific worries, perhaps people can reassure you?