Finally, from experience I've formulated a rule of thumb:

Last-minute edits on a work that has been in progress for a long time, or a published work about to be republished, are mistakes.

Last-minute edits on a work you have very recently completed are likely to be good edits.

If one is "in the zone" of creation on a particular piece, ideas for revision rise from the same pool of thought, or, as they say, "are organic." After that work has been completed and set aside and another work commenced, that same zone simply never comes again. The author has changed or grown and can't step into the same work twice. I have longed to add a new insight to an old work, and did, and now that extra sentence in there jars me, and I am concerned that it might jar readers just as much.

One's old stories and poems can be rewritten or refurbished and turn out very well, but not if rewriting or additions take place at the last minute; say, a few hours before a contest deadline. It's like sewing a new sleeve on an old shirt. It might fit but it will be a slightly darker shade or nap or texture, and even if no one else knows, the author does. Is it too small a thing to care about? Not if you care about craft.

I have the answer.

Brilliance is revision and revision is brilliance.

Brilliance doesn't come in the first draft. Brilliance is accumulated over drafts.

Writers are very lucky because we can take our first drafts and over time develop and craft them. A first draft is like Adam's rib. We add the muscle, nerves, flesh, hair, and breath of life. Editors, publishers, and fellow writers help us polish the work until it shines and communicates perfectly, and keep us from making public our inevitable misjudgements and mistakes. That's why your favorite writers dazzle you. How do they do it? Revision. That's why years pass between their books.

We all want to write brilliant first drafts and be done with it. That's like wanting to climb Everest right this minute without a base camp or a team, or have a baby right now without a pregnancy. That'd be brilliant, but it's unlikely. Don't pressure yourself with the belief that you can or should write brilliantly immediately and all by yourself all the time--that you must be superhuman. That will be unproductive. Revision is very human. The humanity which soaks into the work through revision is what makes it brilliant.

It should be obvious but sometimes isn't: Facts are basic to nonfiction writing. Even a personal essay or memoir relying mostly on the author's memories gains power by using "hard facts" from other sources: photos, reports, quotations, definitions, dates, and interviews. Maps, court records--facts are everywhere, and readers need them to fully enter the world of your essay. But surprisingly, writers of personal essays often don't think to mention what year they are recalling, what town they lived in, the names of their parents and siblings, the name of the rival school (Hamilton? Franklin? Something like that. Does it matter? In nonfiction, yes). They often neglect too even to describe themselves, as they were or as they are.

Some writers arrive at creative nonfiction thinking "creative" means "no research." (After those college research papers, what relief!) But even if you don't use all the facts you find, the ones you do use give your personal essay muscle and traction. Did "your father read books", or did the shelves he built in your basement overflow with his personal library of 200 Civil War biographies and histories? (Research the family photos! Open the old boxes!) Did "your family go to church," or did you and your mother and older brothers Allen and George take a slow-moving city bus every Sunday to the First Christian Church on Maple Street? (How far was it from home? How much was the bus fare? Interview your mother, or look those up.) Trying to recreate your reality in your nonfiction? As you revise, find and share with your readers the facts of who, what when, where and why.

Do it too for yourself, just to own your own facts. It feels like owning gems.

Walter Bargen’s critique of a poem I brought to the St. Louis Poetry Center Workshop shifted my philosophy of revision. He said, You use too many words. Get it going with the first line. Make sure that in every line something happens. Shorten your sentences. Cut every word and phrase not absolutely needed. With these in mind I revised and think I improved the poem. Its first two stanzas will illustrate. See what you think:

Before:

Seekers and pilgrims leave rosaries and coins
at each of the seven grottoes engineered
like sand castles, frenzied
in conception and scale,

each begetting another, life-sized, more sensual:
a stone tent for the slumbering plaster disciples;
for the satiny skins of the plaster Pietá
a stone canopy inlaid with bottle glass and scallop shells;

After:

Seekers and pilgrims leave rosaries, coins.
The seven grottoes engineered
like sand castles, frenzied
in conception and scale,

shelter strangely sensual scenes.
Plaster disciples slumber
beneath a canopy of masonry
chased with beach glass and scallop shells,