I heard you like chumrot so I put a chumra in your chumra.

念には念を入れよ
(Nen ni wa nen wo ireyo;
“Put thought into thought”)

Definition:

An exhortation to be extra meticulous or cautious in a given task or situation. Make absolutely certain that you’re doing things right. Everybody makes mistakes, so take measures to guard against them no matter how careful you think you’re being. “Measure twice, cut once.”

Breakdown:

We begin with the noun 念 (nen), a complex and hard-to-translate word that we’ll translate here as “thought,” marked as the target of some motion by the directional particle に (ni). This particle is coupled with the topic-marker particle は (wa), making “[in]to [one’s] thought[s]” the topic of discussion. The comment on this topic begins with a second 念, marked by the particle を (wo) as the direct object of the verb 入れる (ireru), “to put something into something,” which appears in imperative form.

Notes:

Rendering the final verb in conclusive form (入れる, ireru) is considered an error.

Japanese products tend to have a reputation for high-quality craftsmanship. Setting aside the question of how much this is based on measurable qualities versus stereotypes, we see this reflected in a myriad of phrases that can be considered synonymous with this one, including 浅い川も深く渡れ, 石橋を叩いて渡る, and 濡れぬ先の傘.

This saying is attributed to our friend the Huainanzi (Japanese 『淮南子』 =  Enanji). It is the ね (ne) entry of the Edo iroha karuta set.

Example sentence:

「鍵、掛けたよね。掛けたはずだよね！毎回ちゃんと掛けてるもの、今日だけが違ったらおかしいよね」
「念には念を入れよ、だよ。ずっと悩むより、今すぐ確認すれば良いじゃん」

(“Kagi, kaketa yo ne. Kaketa hazu da yo ne! Maikai chanto kaketeru mono, kyou dake ga chigattara okashii yo ne.”
“Nen ni wa nen wo ireyo, da yo. Zutto nayamu yori, ima sugu kakunin sureba ii jan.”)

[“I locked the door, right? I must have. I always lock it properly; it would be weird if today were different.”
“Better safe than sorry; I’d rather you go check now than worrying about it the whole time.”]