Saying 'no' is always difficult and I've discovered that it is even more difficult when you work for yourself and are convinced that this is the last offer of work you will ever get

First of all, remember that it's always good for people to know that you are busy. It gives the impression that you are in demand because you have valuable skills. Second, it's always worthwhile seeing if there is some room for negotiation if it's something you would like to help with. I was recently offered an editing project (a music psychology book) that I really wanted to do, but couldn't possibly fit in at the time. I explained this to my client and told her when I would be able to fit the work in.

A day later she called me to say that she had rescheduled the production date for the book so that I could edit it.

So, it's always worth discussion/negotiation to see if you can find a win-win solution.

Sarah