It distracts from the now.

後悔先に立たず
(Koukai saki ni tatazu; “Don’t put regret in front.”)

Definition:

An admonition: Don’t regret things that are over and done. Don’t spend time ruing something that can no longer be changed. “Don’t cry over spilled milk.” It is better to spend extra time and effort being careful before anything bad happens than losing the same time and energy to regret after it happens.

Breakdown:

We have a brief but complete sentence here. The verb is 立つ (tatsu). Generally translatable as “stand,” this form is only used intransitively in modern Japanese (the transitive form is 立てる), but classically it could be used either way. The verb appears in imperfective form with negative suffix ず (zu) in sentence-final form. The “location” of the verb is indicated by the particle に (ni) and specified by the noun 先 (saki), “before,” “front,” “future.” Finally, although it’s not marked as such by any particle, we’re given the object of the verb, the noun 後悔 (koukai), which can be translated as “regret,” “remorse,” or even “repentance.” The subject (the person being addressed) is implied rather than explicitly included.

This doesn’t come out well in translation, but I’m tickled by how the 後 in koukai means “after,” while 先 means “before.” It might just be a linguistic coincidence, or it might be the whole point of the saying, but it serves to emphasize how nonsensical it can be to go on inserting the past into the future by keeping regrets in mind.

Notes:

That said, I disagree with the tenor of the above paragraph, to an extent. Regret itself is not inherently nonsensical, nor is it necessarily a waste of time. It’s a tool that evolution left us with. I believe that regret is all about remembering how one’s actions led to an undesirable outcome, and its purpose is to help us avoid undesirable outcomes by not repeating those actions. Regret, used correctly, is a spur to make you inspect your own actions and methods and do better next time. In short, as I try to suggest with the last line in the “definition” section above, regret should be part of the backdrop against which you plan for the future, instead of being held in front of your face so that it blinds you.

Some versions of this saying expand the compound noun 後悔 to 後の悔い (nochi no kui) – the exact same content presented in a less Chinese-like style. One of my sources gives a comma between 後悔 and 先, although it’s not necessary and I wouldn’t recommend it. Replacing 立つ with 建つ, a homophone of somewhat similar meaning, is considered an error.

Apparently some versions go on with a second clause that warns against putting one’s lantern-bearer behind one, but to be honest I feel like this confuses the issue by introducing either an outdated and unrelated specific warning, or by suddenly throwing an unclear metaphor into what was previously a clear statement.

Example sentence:

子供の頃から何度も失敗して後悔を激しく覚えて来た美智子であったが、その日、後悔先に立たずと積極的に頑張ることを心の中で誓った。

(“Kodomo no koro kara nando mo shippai shite koukai wo hageshiku oboete kita Michiko de atta ga, sono hi, koukai saki ni tatazu to sekkyokuteki ni ganbaru koto wo kokoro no naka de chikatta.”)

[“Since her youth, Michiko had erred time and time again and had known fierce pangs of remorse. But that day, she swore to herself that she would forge forward without letting regret get in the way.”]