過ぎたるは猶及ばざるが如し
(Sugitaru wa nao oyobazaru ga gotoshi;
“Too much is the same as not enough.”)

Definition:

Overdoing something is ultimately the same as not doing it enough. For most human endeavors there is a happy medium range, and going beyond that range is no better than failing to reach it. You can have too much of a good thing, and it can be just as bad as a lack.

Breakdown:

We have a complete, and grammatically complicated, sentence! It ends with the auxiliary verb 如し (gotoshi), “the same as,” “like,” in sentence-final form. (It make take a moment to realize that it is in fact a verb, because it inflects as if it were an adjective.) It’s preceded by the particle が (ga), which in classical Japanese serve the function more familiarly filled, to modern learners, by の (no). But what is its actual grammatical function, besides being “the thing that precedes 如し”?

I believe that the function is actually a normal noun-association. Bear with me for a moment. The が connects our auxiliary verb to the preceding verb, 及ぶ (oyobu), “to reach.” This verb is in the imperfective form so that it can be attached to the negative suffix ざり (zari), itself in attributive form. And all of the above is shown by the topic-marker particle は (wa) to be modifying the verb 過ぐ (sugu), “to pass,” “to exceed.” This verb is in the conjunctive form, and appended by the auxiliary verb たり (tari), again in attributive form. Meanwhile, between the は and the second verb we find 猶 (nao), an adverb that in this case means something like “likewise” or “too.”

You may note that there are no nouns in this sentence, but that the verbs are not being treated grammatically as we would normally expect. The attributive form here seems to be signaling that the verbs are to be treated as nouns. (It’s not clear to me offhand whether this was simply how nominalization was signaled in classical Japanese, or whether it’s shorthand for a structure similar to modern [verb]+こと.) But in the end, we can take the above and render this saying as “Overdoing is the likeness of not reaching,” and in that light our no-like ga makes sense to me.

I am of course open to hearing from any Japanese grammarians who have a more accurate explanation!

Notes:

It’s acceptable to leave out the nao; this doesn’t significantly change the meaning.

This is another kotowaza derived from the Analects; in this case, from the Xian Jin (先進) chapter.

There are a number of variant sayings on the same theme. Several of them are more situation-specific, e.g. declaring that over-politeness is the same as impoliteness, or that too much prudence is a form of foolishness.

Example sentence:

「どんなに野菜は健康にいいと言っても、過ぎたるは猶及ばざるが如く、毎日サラダばっかり食べるなど、やっぱりちょっと．．．」

(“Donna ni yasai wa kenkou ni ii to itte mo, sugitaru wa nao oyobazaru ga gotoku, mainichi sarada bakkari taberu nado, yappari chotto….”)

[“It doesn’t matter how good vegetables are for you; you can have too much of a good thing, and just salad every day is a bit much!”]