子を持って知る親の恩
(Ko wo motte shiru oya no on;
“The kindness of a parent, which you realize when you have a child”)

Definition:

Raising kids is hard. But as with most difficult tasks, most people don’t realize the exact amount of time and effort that it takes until they’ve tried it themselves. As a result, most people only realize the full depth of the debt of gratitude they owe their own parents upon becoming parents themselves.

Breakdown:

We begin at the end, with the noun 恩 (on), “kindness.” Associative particle の (no) marks it as being the kindness of 親 (oya), “parent(s).” The whole kotowaza is a noun phrase, further modified by a verb phrase ending in 知る (shiru), “to know.” The circumstances of this knowing are explicated by a nested verb phrase ending in the verb 持つ (motsu), “to hold,” or by extension, “to have,” appearing in conjunctive form. The particle を (wo) marks the noun 子 (ko), “child,” as the direct object of motsu. And there you have it!

Notes:

Variants replace 持つ⇒持って with 育つ⇒育てて (sodatsu⇒sodatete), rework the message into a double negative, specify mother and/or father, or make other changes.

This saying reportedly comes to us from Chinese Zen biography anthology The Transmission of the Lamp (景徳傳燈録, Keitokudentouroku) via 14th-Century CE Japanese essay collection Tsuredzuregusa (徒然草).

Example sentence:

孝衛は散々歩き回って竟に赤ん坊を寝かせてから、子を持って知る親の恩を深く知ったような気分になって、自分の両親に祝いがてらプレゼントを送ろうと決心した。

(“Takamori wa sanzan arukimawatte tsui ni akambou wo nekasete kara, ko wo motte shiru oya no on wo fukaku shitta you na kibun ni natte, jibun no ryoushin ni iwai gatera purezento wo okurou to kesshin shita.”)

[“Having finally put the baby to sleep after a great deal of walking around, Takamori felt that he deeply understood the debt of gratitude owed to one’s parents that only a parent understands. He decided to use the celebration as an excuse to send them a present.”]