We all know what he meant. And the sentence actually sort of says it. BUT!
I try to discourage students from beginning sentences with “There are” (or “there” plus any verb of being, seeming, or becoming). In a language the most common sentence structure of which is subject-verb-object, readers and writers alike generally place the most emphasis on the first two or three words of a sentence. The “there are” structure uses what I call a “place-keeper word” (Webster’s labels it a “function word” but I’m more basic) in the position of, and in the grammatical role of, the subject and follows it with a verb that is no more than an equal sign, a static rather than active word. So the writer blows the main engine of the statement as the reader idles, waiting for the noun that is the conceptual subject of the sentence to complete the equation and open into an adjective clause that may actually say something. There are times when such a structure is useful (voilà), but it is never interesting or energetic. And still my students, perversely smitten by sheer love of it, use it again and again—I’ve read essays where two thirds of the sentences began “There are” or “There is.” (A lot of the rest began “This is,” a weak structure for some of the same reasons and some others as well.)
Having begun “There are,” this student must stagger forward: “only so many chances.” How many? Well, perhaps we can accept this phrasing, which while refusing to state the limit at least establishes that a limit exists.
Now we have to make clear that these chances don’t merely sit waiting for something to happen; they are conferred, or conceded, or granted, or permitted. Let’s take the most boring of all the possible terms and say “given.” It doesn’t really matter: any choice here is going to have the same weakness, which is that it’s going to be a past participle of an action verb, which means the reader becomes curious about who is doing the conferring, conceding, permitting, granting, or giving. In other words, to the static sentence we have now added a note of passivity.
Instead of providing someone to do this giving etc., my writer has shifted his focus to another invisible unexpressed entity, one engaged in doing a present participle: “making mistakes.” Mistakes are being made, and chances are being given. By whom, and by whom? And the chances are evidently being given while the mistakes are being made, which isn’t what the student really had in mind, I don’t think. But consequently, we have to wonder if the chances run out before or after the mistakes have finished being made.…I suppose this suspense might be considered a type of engagement, something the sentence otherwise resists.
But he pushed through his sentence somehow, and now he’s done and can place that period, that dot of relief, and move on to another thought. Whew.
So what did he mean? Easy: Three strikes and you’re out. Or: Keep starting your sentences with “There are” and eventually the professor is going to run out of patience and flunk you. Or: Surgeons who can’t tell “right” from “left” are going to run out of patients.