But now more than ever, I apply the life-is-too-short test: Would I rather be home getting work done, drinking my own coffee, reading a book or watching Hardball than having breakfast, lunch, or dinner with this person?Experience has identified and jelled another inclination, and that is honest self-assessment of my dependability. For example, phone calls come in from various national charities, asking not for my money but for my time. Will I address envelopes and deliver them to my neighbors on — the caller pauses, checks her list — "Winterberry Lane?" I used to say yes. Now I say, "I’m a very bad candidate for this. I’m not reliable. You’d send me the envelopes, and they would just sit in a pile of mail. Really, you could do much better."A disclaimer: I still do say yes a lot. There’s nothing better than a night out with good friends involving good food. Only a bona fide conflict would keep me home from dinner with my nearest and dearest. A prime example of that would be any social summons from our son, now 24, whether he’s coming East or we’re crossing the country to visit him.Not quite as tempting are certain professional obligations. Because my first novel came out 16 years ago — coincidentally, the same year I turned 40 — I’ve had a long time to sniff out what may be the less-desirable venues, which is to say the readings where nobody comes and/or the attendees aren’t — as my late mother would say — from the book buyers. When invited to those events where I would be a keynote speaker at the annual meeting of the Friends of Any Given Library or X Worthwhile Charity, I have learned to ask, "Would it be all right if I arrive after the, um, business items?"Experience has taught me that I am not always interested in the raffle of items donated by local merchants, or last year’s minutes, or this year’s awards and thank-you gifts to the hardest-working cochairs without whom…, and so on. Accordingly, I inquire in advance, "Your event begins at seven o’clock? And what time, might I ask, would I actually be needed?"I don’t want to be seen as a diva and certainly want to be a trouper on behalf of my publisher and our mutual wares. More social algebra: Will I flop, or will I draw a crowd? What if I say no and I’m wrong? Can I ever really be sure what to accept and what to decline? Yes, if I’ve done the event in the past and know it’s a dog. Take the pre-Christmas bookstore sale-a-thon where at least 10 authors sit with their works, thereby encouraging customers to confuse the event with a crafts fair. They browse; they pick up your book, turn it over, read the flap, compare the photo to the live person in front of them, smile weakly — then move on to the best-selling author two chairs down. The first time I attended, I consoled myself that there was a payoff: the deli downstairs had corned beef and chopped liver and really good pickles. Second year, I brought my knitting; the same year I noticed that the paperbacks piled at my station had been signed by me at the first author-thon. Third year, I declined, and I told the truth: too many authors, not enough customers, snow predicted.Sending Regrets and Not Regretting ItA fellow author tells me that I once intoned, "You never regret saying no." She reminded me of this recently when I told her I’d accepted an invitation to keynote a writing retreat in New Hampshire and to stay for two nights."I’m surprised you said yes," she scolded. "In fact, I keep your advice on a note by my computer: ‘You never regret saying no.’" "There was a clincher," I told her.She waited."They’re sending a car to get me. And it’s at a spa.""Got it," she answered.As I’m turning someone down, the good girl inside me winces. But almost immediately after I’ve uttered, "I’d love to, but…," I feel relief — and something akin to backbone. Ahead of me lies one less obligation, one less sticky note on my screen saver, one less trip to plot on MapQuest. My calendar thanks me: A blank day means I write all morning in my pajamas, savoring the dividend of calling my time my own.I have a companion quirk to the saying of no: I must explain why I’m turning down an invitation. I always respond with an excellent reason, fiction or nonfiction, and I ask the same in return.