When the student is ready, the teacher appears.

She seemed ancient at the time, though as I read her recent obituary, I realize that she must have been relatively young. It was years before I could remember my tutelage under the firm, unflappable eye of Marie Lufkin without a painful jab to my pride. To contemplate her sainthood on All Saints Day, it is necessary to set aside the notion of saints as soft-focus faces on holy cards, as bearers of light. Marie Lufkin, RSCJ, introduced me to the far more pungent truth: Our truest saints are those who cause us to run headfirst into a wall. Several times, if necessary, until we learn how to climb over or walk through it, bruised and wounded, into fuller lives.

I met Mother Lufkin in her 9th-grade classroom. She was teaching history at my girls’ convent school, and I was a dreamy 15-year-old. My attention in those days operated on a sort of wave cycle. My interest lasted the first 10 minutes, then shifted into a kind of reverie in which, as her voice continued on, I moved up and down the crest of my interior conversations. The bell rang, and I moved on to French class.

French, English, math, and science, all proceeded along a predictable rubric. Short-term learning goals were set each day, and were easily achieved with average diligence at night. Most of us ended the school week feeling snug as bugs about our progress; eager to defeat the next field hockey team to wander onto our playing fields, and full of anticipation of Friday night’s dance at the boys’ school. My identity as a straight-A student was so internalized by then that I never thought about grades.

But the sainted Marie Lufkin — fervent, disciplined, orderly, intellectual — had other designs. That fall, she assigned a 10-page term paper. We learned how to use the Dewey decimal system, research sources, make note cards, write outlines. I’d decided that my topic would be the Russian Revolution — all of it. I can still see myself in the little study space my parents had carved out for me off the kitchen the night before it was due, feeling a bit overwhelmed and uncertain before the plethora of notecards strewn about, the lateness of the hour, the baggy feel of the document that I managed to produce, well after I was normally in bed. Still and all, in my usual optimist dreamscape, I was pleased with the scope of my ambition and believed that earnestness would win out.

The papers were returned a week later. On the last page of mine, I discovered, in bright red ink, a very large, very unambiguous F. No other comment, as if the whole enterprise had been beneath contempt.

The hot white glare of divine damnation froze my entire being. My mouth went dry. My heart pounded. I was stupefied, mortified. The shock temporarily paralyzed my ability to read her marginal comments. Dust had returned to dust far ahead of schedule, and I crept off to my next class a shriveled crumb of castoff humanity.

For a week I shuffled into class last of all the girls, and sat in the back row with my head bowed. Devastation had turned to shame.

Years later, when I discovered the practice of Zen Buddhist monks who strike their students on the head with wooden sticks when they sense them drifting into complacency, I realized what Marie Lufkin had been trying to accomplish. She’d had to drag me off my little mountain of self-assurance, my adolescent know-it-all posture. She wanted me to grow up and face myself — my capabilities and talents and, equally, my responsibility to them. No one had held me accountable until she did, and it changed my life.

Picking myself off the floor and going in to see Mother Lufkin was one of the hardest things I’ve ever done. It took real effort to change my slovenly study habits, and an attitude that said no one would notice if I gave 50 percent and left the rest to charm.

There have been times in the years since when I’ve taken on more than I should, but never again have I given less than 100 percent to the effort. I survived Marie Lufkin’s class, and started the high school newspaper. I wrote my way through college, editing the college newspaper and publishing fiction and poetry. I became an author and a teacher of writing. I am convinced that none of this would have happened without the painful grace bestowed by my toughest saint, Marie Lufkin.

She turned it all upside down, this staunch and uncompromising woman. She taught me that saints are those who shake us out of our complacency, force us to grapple with real engagement and real intellectual challenge. Like the desert fathers, Martin Luther King Jr., Ta-Henisi Coates, Dorothy Day, she disrupted my pride, my sense of entitlement, and my conventions. Painful though it was to be hit over the head, and countercultural to our success-obsessed norms, I learned the great power of failure.

I look at Marie’s obituary photograph. The soft smile and the kind eyes are very real. But my thanks and farewell are not for these. They are for the toughness and love that led me deeper into discipline and faith than kindness would ever have done.