善は急げ
(Zen wa isoge; “Hurry to do good”)

Definition:

“Strike while the iron is hot.” Specifically, if you think of something that would be good to do, something worth doing, something worthy – do it now. Don’t wait. Don’t procrastinate. If you have a good idea, a new year’s resolution, a plan – do it now! You can come back and finish reading this post later, I promise. (If your idea is “study more Japanese,” of course, please stay: that’s what you’re already doing.)

Breakdown:

善 (zen) is a noun meaning “virtue,” “good(ness).” It’s followed by the topic-marker or emphatic particle は (wa), and the transitive verb 急ぐ (isogu), “to hurry (something)” in imperative form. An obsessively literal rendition might go “As for good(ness), do it quickly.”

Notes:

The phrase can be extended by adding its inverse, 悪は延べよ (aku wa nobe yo), “delay doing evil.” In this phrasing, the first は should probably be interpreted as emphatic, and the second (the は in 悪は) as contrastive. Finally note that, in Japanese if not in English translation, this saying is considered antonymous with 急がば回れ.

Example sentence:

「明日から、毎日ジョギングすることにした」　「あ、良いね。これからでも一緒にしない？善は急げだよ」

(“Ashita kara, mainichi joggingu suru koto ni shita.” “A, ii ne. Kore kara de mo issho ni shinai? Zen wa isoge da yo.”)

[“I’ve decided that I’ll go jogging every day, starting tomorrow.” “Oh, that’s a good idea! Why not do it now, together? ‘Strike while the iron is hot,’ you know.”]

You’re not going to argue with the best captain, are you?