Think too long and your judgment goes stale.

The source

"Think too long and your judgment goes stale." Yamamoto Tsunetomo said it in Hagakure, Book 1. Translated from the original Japanese by Spartan Surfers.

"分別も久しくすればねまる"

Original Japanese, Hagakure, Book 1. Japanese: Hagakure, vol. 1 (1937 printing), NDL digital text; Saying of Ryuzoji Takanobu quoted in Hagakure.

Who said it

Yamamoto Tsunetomo (1659–1719). Samurai turned monk whose spoken reflections were written down as Hagakure, Hidden by Leaves.

Questions

Who said "Think too long and your judgment goes stale."?

Yamamoto Tsunetomo (1659–1719). Source: Hagakure, Book 1.

What is the original Japanese?

分別も久しくすればねまる. Translated from the original Japanese by Spartan Surfers.