I think it is important to take a business-like approach to freelancing from the start: you make your life much easier in the long run. Set yourself some realistic working hours. Build in breaks and make it a strict rule to turn off the pc at the end of your work period. It is all too easy to end up burnt out. Obviously there are always exceptional deadlines, but if you can keep work for weekdays and evenings and weekends to relax you will feel better and work more effectively too.