Oh.

急いては事を仕損じる
(Seite wa koto wo shisonjiru; “To hurry is to fail”)

Definition:

If you rush things you’re going to make mistakes, and your attempt at speed will end up having been in vain. When pressed or pressured, be extra careful. Haste makes waste. 急がば回れ.

Breakdown:

We begin with the verb 急く (seku), “to hurry,” in conjunctive form. The combination of the “te” form and the following particle は (wa) creates a conditional, “If you hurry.” The clause describing the consequence begins with the noun 事 (koto), “thing,” “matter,” “situation,” etc. The “matter” is marked as the direct object of a coming verb by the particle を (wo), and that verb is 仕損じる (shisonjiru), “to make a mistake” or “to fail,” in sentence-final form.

Notes:

The final verb may appear in alternate form 仕損ずる (shisonzuru) or be replaced entirely by 過つ (ayamatsu), “to err.” However, while the kanji 急 is also used in the verb 急ぐ (isogu), reading the opening of this saying as Isoide wa would be an error.

This saying apparently comes to us from an 18th century Chinese text called the 通俗編 (in Japanese, Tsuuzokuhen).

Example sentence:

「石に躓いて倒れながら、大事に抱えていた焼き物がきっと飛んで行ってしまうと実感した渉君の脳裏に浮かんだたった一つの考えは、ああ、何度も耳にしたことはあるけど、これでようやく急いては事を仕損じるという言葉の意味が理解できた、ということであった」

(“Ishi ni tsumadzuite taore nagara, daiji ni kakaeteita yakimono ga kitto tonde itte shimau to jikkan shita Wataru-kun no nouri ni ukanda tatta hitotsu no kangae wa, Aa, nando mo mimi ni shita koto wa aru kedo, kore de youyaku seite wa koto wo shisonjiru to iu kotoba no imi ga rikai dekita, to iu koto de atta.”)

[“He tripped on a rock and as he fell, as he realized that the pottery he had cradled in his arms so carefully was going to go flying, the one thought that flitted through Wataru’s mind was ‘Oh, I’ve heard it over and over, but now I finally understand the meaning of the phrase Haste makes waste.’”]