Between Civil War battles in early 1864, Clara Barton was stuck in Washington with time on her hands. She was mentally exhausted by physical inactivity during a winter pause on the front, and frustrated that her latest effort to open a new warehouse for supplies hadn’t panned out.

“I am depressed and feel dissatisfied with myself,” she wrote in fine, tiny script in diaries now stored on microfilm in the Library of Congress. With so little to do, she paradoxically couldn’t rest, and so “rose not refreshed, but cold and languid.” For neither the first nor last time, she considered suicide.

“All the world appears selfish and treacherous,” she wrote on April 14. “I can get no hold on a good noble sentiment any where. I have scanned over and over the whole moral horizon and it is all dark. The night clouds seem to have shut down — so stagnant, so dead, so selfish, so calculating. … Shall the world move on in all this weight of dead, morbid meanness?” A few days later, she fantasized again about killing herself.

But then, as Elizabeth Brown Pryor wrote in her 1987 biography, “Clara Barton: Professional Angel,” the self-made philanthropist’s “dejection was lifted finally by her only true remedy — a need for her services. The Union army’s spring campaign had started early.”

When every single man assisting at a surgery in Antietam ran for cover under fire in 1862, Barton had not only stayed but gloried in having bested the boys; the sort of duty that incapacitated others brought Barton back to life. And so, in spring 1864, with the death of thousands in the woods of Spotsylvania County, Va., she restocked supplies and was off again to care for the wounded. Not long after, a co-worker saw her, according to Pryor, “as a cheerful spirit, breezing through the wards in a blue dress and white apron, rousing the men by singing ‘Rally Round the Flag, Boys.’ ”

Throughout Barton’s long, difficult and staggeringly successful life, she self-medicated through service, her diaries reveal, using the most intense, bloody work imaginable to keep the “thin black snakes” of sadness from closing in. And, fortunately for Civil War soldiers, women voters, anyone who has been helped by the American Red Cross, and every G.I. who ever wore a dog tag, Barton did not take her own life — and instead died of pneumonia in her Glen Echo home 100 years ago this week at age 90.

Her obituary, which made the front page of the New York Times on April 13, 1912, said: “Clara Barton was President for twenty-three years of the Red Cross Society, which was established in this country through her efforts. She retired in May, 1904, on account of factional quarrels within the organization. But long before the society was founded she had become famous for her work on battlefields in the civil war and in the Franco-Prussian war.”

Indeed, it’s hard to imagine how Barton could have accomplished more. And easy to wonder if a happier woman would have fought as she did — with presidents and nobodies, over great injustices and petty slights.