How To Say No. Politely, Of Course.

Dear Mrs. Ditter: I am desperately wondering how to say no when people ask me to do stuff all the time. I work from home (or 'work' as people call it, writing apparently not really being work. I recently almost poked one of my brothers-in-law in the eye over this exact point, but restrained myself--didn't want to spoil a family wedding!).  I'm asked to do every voluntary thing in South-East England and I am hopeless at saying no. So now I end up working more hours than I did when I was working in a science lab all day! Help! -- Spineless Writer
Dear Spineless (which I suspect you are not): You are such a nice person, and such a competent one, as well. How do I know? Because people are asking you to do stuff! That means you're good at getting stuff done, and you're polite to people. Admirable qualities, indeed, but perhaps not what you need at the moment.
Now, before irate readers write in demanding equal time for the importance of volunteering, let's remind ourselves that people take on unpaid work for many reasons--some admirable, some more questionable. Many people volunteer because of the strokes they receive for being perceived as selfless, generous, and dependable. Some people volunteer because of the warm fuzzies they experience when making a contribution to something bigger than themselves. And some volunteer because their parents raised them that way. The point is, Spineless Writer clearly has done her share of volunteering. She needs to get back to herself.
So, okay, ready? Let's start with a quick review of Mrs. Ditter's Four-Step Program to Polite Assertiveness and Happiness.
First, remember the following four things:
Saying NO is not mean, dishonorable, petty, or selfish. 
Saying NO can be done in an empathic manner ("Oh, I hope you find someone to watch little Bobby. I understand that you need a break.")
Saying NO can be done without being rude or aggressive ("Why the heck would I want to help with that project?").
Saying NO can be life-affirming and uplifting. Seriously! It opens up emotional and physical space for you, and allows you to attend to yourself and your current responsibilities.
Second, practice these two things:
A) Speech therapy. Here's what you do: Find a private space (it can be a quiet room, a closet, the shower, a barn, whatever). Now, stand up straight, take a deep breath, and practice saying the following things out loud: "NO. I can't. No, I can't help with that. I'm on deadline with my book. I'm already fully committed. No, I simply don't have the time available."
How convincing did you sound? Yeah, I thought so. Get back in the barn and try it again, more sincerely this time. Really put some truth and energy into it. If you don't believe the words coming out of your mouth, neither will the people who are listening to those words and waiting to pounce at the first sign of weakness.
B) Visualization. Quit rolling your eyes! This really works, IF you give it a chance. Get comfortable either sitting or lying down, and watch the following movie in your head: Your phone rings, you pick it up, The Voice on the other end says, "Spineless! So glad you're in. The village council has a project that needs handling, and you're the PERFECT person for it." Here's where you stop The Voice cold: "Thank you for asking, but I'm fully committed right now and can't help out. I hope you find someone else to take on the responsibility."
Want to watch another movie? How about the one where you're cornered in the drugstore as you're reaching for feminine sanitary supplies? Roll that movie, too, and as your hand reaches out toward the Tampax, hear The Voice: "Darling, so glad I ran into you. The school board all agree that you're the ONLY person who can run the auction for this year." And now watch and listen as you say, "What a compliment, but I'm extremely busy. I simply don't have time to take on any more responsibility."
Play those scenes, or whatever scenes are most likely to reflect your situation, over and over until you can refuse a request in your sleep.
Third, delete these phrases from your vocabulary: "I'm sorry. I wish I could. Please ask me the next time you need help." 
Why? Because those phrases are not honest, and they take away from the power of your honest NO. You're NOT sorry. You DON'T wish you could help. You DON'T want them to ask you next time they need assistance.
Just how you go about deleting them is up to you. I suggest writing each phrase on a piece of paper and then setting fire to it. Woohoo!
Finally, you absolutely are NOT allowed to say: "I suppose I can squeeze it in. Yes, I can help." Write these down, douse them in gasoline, and light them up. Or...whatever method you choose. Perhaps something less violent would work for you.
Of course, eventually you'll come across something with which you really, truly, honestly want to help. And when that happens, you can say YES with an open heart and a joyful spirit. Until then, practice the power of an honest no.
Best of luck!
Questions for Mrs. Ditter? Leave them in the comments section, below.