自慢は知恵の行き止まり
(Jiman wa chie no yukidomari; “Pride is the dead end of wisdom”)

Definition:

When pride has taken root, arrogance follows and prevents further advancement. A lack of proper humility and modesty blinds people to their own faults and weaknesses, which prevents them from actually addressing those weaknesses and thus growing stronger. Improvement depends on not being so full of yourself that you see no need or room for improvement.

Breakdown:

We begin with the noun 自慢 (jiman), “pride” or “boasting,” marked as the topic of discussion by the particle は (wa). The comment on this topic is a noun phrase beginning with noun 知恵 (chie), “sense,” “wisdom,” or in religious terms, “insight that leads to (Buddhist) enlightenment.”

Next comes a noun built of compounded verbs. The first verb is 行く (yuku), “to go,” in conjunctive form. This is followed by and combined with 止まる (tomaru), “to stop (moving),” also in conjunctive form, which allows it (and thus the whole compound) to function as a noun. As a whole, 行き止まり (yukidomari; note the voicing on the to) refers to “the point at which something stops.” This noun is connected to the preceding 知恵 by the associative particle の (no). At the end one may imagine an elided copula or other sentence-completing structure.

Notes:

行き may also be read as iki without any change in meaning.

This isn’t our first kotowaza warning that pride gets in the way of excellence.

Example sentence:

自慢は知恵の行き止まりだと悟って、「自分は何も知らない」と言い張ったソクラテスは、結局のところ、少しも自分の才能をひけらかさなかったのでしょうか。

(Jiman ha chie no yukidomari da to satotte, “Jibun wa nani mo shiranai” to iihatta Sokuratesu wa, kekkyoku no tokoro, sukoshi mo jibun no sainou wo hikerakasanakatta no deshou ka.)

[Realizing that pride is the end for wisdom and asserting that “I know nothing,” wasn’t Socrates ultimately showing off his own ability, just a little?]