How to say regrets [I should not have X]?

Question

How in the world does this: > 晩ご飯を食べるんじゃなかった。 translate as "I should not have eaten breakfast"? This roughly translates as "It was not that I eat breakfast."

Answer 1

Yes, “I shouldn’t have X” is “x するんじゃなかった” in Japanese. That’s correct. We usually use it in the verbal sentence with んじゃない present tense of んじゃなかった. Also, this んじゃなかったexpression is tend to be used in talking to myself. Sometimes we say “xするべきじゃなかった” in verbal, since “should not= べきじゃない, べきではない( a little more formal)” We use “xするべきではなかった“ in both verbal and writing.

Another way to express to regret, “x しなきゃよかった” “xしなければよかった”

For example, I should not tell him. 彼に言わなきゃよかった。more formal, 彼に言わなければよかった。

Answer 2

晩ご飯 is supper, dinner

食べるんじゃなかった is 食べる(dictionary form of eat) ＋んじゃなかった (should not have)

I should not have eaten supper (dinner).

Dictionary form of verb + んじゃなかった is used to express regret of action taken in a past.

Ex.

行くんじゃなかった (I should not have gone=I regret going)

来るんじゃなかった (I should have not come=I regret coming)

I hope this helps.