The greatest TA I’ve ever had once told me he “did a victory dance” when his advisor got tenure. We were discussing English professors, and his happy relief reminded me of how my favorite teacher and one-time advisor went on leave in the middle of my junior year and never came back. He nodded in commiseration. “You have to grab hold of them,” he said, “before they turn into vapor.”

He was being a bit dramatic, maybe a little solipsistic — for the most part, departing professors are simply moving on to other jobs in different places — but in his excess he expressed something essentially true about the student’s experience of junior faculty transience: As Yale professor Louise Glück says, “These things we depend on, / they disappear.” The sudden, unceremonious severance of a pedagogic relationship can be unpleasant, and I’m not sure the occasional e-mail exchange doesn’t ultimately make things worse. It’s true that not every departure is a tragedy — I’ve been glad to see a professor go — but one feels burned by the system when a gem like Laura Frost goes away.

I met her at the start of the 2006 spring semester, when she taught a seminar called “Narrative and 9/11.” By that time, I had been suffering for several years from a kind of traumatic fixation on the World Trade Center attacks; as a result, I got into the class, did all the reading, talked a lot and, in general, performed well. The following semester, she offered a senior seminar on James Joyce, a writer whom it is all but essential to read in a classroom setting. The first meeting was packed, overflowing. As she had done the previous semester, she asked each student to tell her briefly, in person, why he or she wanted to take the course.

She admitted me, though I was only a junior, and a couple of others who weren’t senior English majors. Since a few students who were didn’t make her cut, she soon found herself in some degree of hot water with the department. “This is probably the last time I’ll be teaching this course,” she told me. She wanted to admit whom she wanted.

Those seniors who complained were right to feel robbed. Our discussion of Ulysses was an intellectual rapture — for as long as I prepared the reading assiduously. Because even though professor Frost had done me such a favor in admitting me, about halfway through the semester I began to blow it. (There was a neat division: before and after the meeting I slept through.) I got caught up in useless interpersonal psychodrama, against which she had warned me. I turned in an unfocused final paper one day late, despite her repeated warnings about how long it would take and how she was leaving the country the day it was due. She graded me forgivingly. Professor William Deresiewicz would have something withering to say about this, if he weren’t gone too.

I have no idea if professor Frost wanted to stay at Yale. But by the time I met her, eight years into her appointment, she didn’t seem to consider such an outcome possible. Yale had recently tenured a different modernist; maybe the marginalia was on the wall. Either way it’s a shame. She was a fantastic discussion leader. Her first book — the stimulatingly named “Sex Drives” — won Yale’s Heyman Prize, and she received a second award for her teaching. Strange, then, that departure seemed a foregone conclusion. Things turned out well for her — she’s now a tenured professor and chair of literary studies at the New School — but I can’t imagine Joyce at Yale without her.

Of course, not every great professor needs to be here. There are lots of good colleges, and all need worthy teachers. I’m sure some faculty members are happy to move on after their initial stints. But imagine starting life as an assistant professor at Yale: You’ve done extremely well in a punishing job market, but now you work, think, even exist under the awareness that your colleagues are your judges as you assay the job of professional smart person. Forget “publish or perish” — your every utterance is up for evaluation. The corollary of this intense insecurity is exemplified by my TA’s victory dance. His advisor’s tenure review could have just as easily gone the other way.

I took last semester off to get my act together; now I’ve got this one left. But no amount of academic atonement can reach back and touch my past mistakes: Professor Frost is gone, and when she left she took with her a finished picture of me as a student. The only thing I might still embellish is the picture I hold of myself. Last week I ran into a recent Yale graduate, back from his Marshall Scholarship, and I asked him if I should take a class with a certain English professor. He told me, “Yeah, if you want a spiritual father who will demand the best of you in the eyes of God.” And as it happens, that’s exactly what I want, though of course she could also be a mother.