Two years ago I lived at the edge of Manhattan’s Upper East Side. Each weekday morning at 6:30 I caught the uptown train, which shuttled me through subterranean corridors to the enormous Bronx public school where I taught kindergarten. Most mornings I praised myself for tackling such a difficult job. The rest of the time, a different thought haunted me: as a teacher, was I doing enough? Some days, I felt like an excellent educator. Other days, I believed my effort betrayed me for what I really was: mediocre. Teachers can’t easily define success in the workplace. We don’t toil at investment banking firms and gauge a job well done by the number of zeroes on a holiday bonus check. Or sell enough office furniture to win a trip to Aruba.

So how did I measure my accomplishments in the classroom? When Zakaria, a saucer-eyed boy from Senegal, began talking after months of anxious silence? When Ivanny used her phonemic awareness skills to write about me: She les us do fun stuvf togethr and she reed books to us and she is reel reel nis sumtim? When Roger’s mother tearfully thanked me for treating her son like my own?

Or should I consider my mere presence in the room “enough”? I hiked in on snowy days. I wore colorful clothes and a perennial smile. During snack time I encouraged my students to find the letter of the day on their Capri Suns and Nutter Butter wrappers. I passed up happy-hour drinks with friends and never gave my children worksheets while I recuperated at my chipped desk.

But I did party on the weekends. I often left lesson planning for Sunday afternoon, quickly creating activities to fill 25 hours of teaching time each week. I locked my classroom promptly after dismissal on Tuesdays and Thursdays, caught the train home in time to hit the gym and cook dinner before Access Hollywood began. Some days, I didn’t teach math. I brought leaves to the classroom during fall, used cotton balls and white paint to re-create snow in winter, and ordered caterpillars—watching them cocoon and emerge as butterflies—in spring, but that was the extent of Room 302’s science curriculum.

During my second year teaching, the vice principal purchased nifty, grant-funded Palm Pilots, which my colleagues and I used to monitor our students’ literacy skills every six weeks. From September to June, I saw the number of names under my “at risk” column dwindle to one. Finally, I had hard evidence of my success. Meanwhile, exposed were the teachers who failed their students (not surprisingly, the same ones the rest privately chastised for their sloppy classrooms and lax discipline). Still I wondered: sure, I taught my students to count syllables and blend sounds, but was that enough?

Now I live in Cambridge. I packed up my classroom after three years of teaching to go back to school. I couldn’t face a career of redecorating bulletin boards each month, unclasping tricky Bratz belts while little girls squirmed to hold in their pee, and screaming at little boys to stop throwing crayons across the room. The decision was made one sticky May day after a failed addition lesson, when Cory spat in Ladesha’s face and my patience evaporated into the hot air.

But since I left I’ve realized a few things. For one, patience is a renewable resource. No matter what happened the day before, I revived loyally each dawn. Each morning I greeted my students with replenished serenity. When in command of 22 five-year-olds, part of me thinks exercising patience is giving them more than “enough.”

I’ve also realized that altruism is somewhat selfish and addicting. I missed those small palms pressed adoringly into mine. And after a brief hiatus, I’m back—teaching children part-time. Am I doing it just to feel good about myself? Does it matter?

Katherine Newman, a former New York City Teaching Fellow, teaches writing at Emerson College in Boston.