■ I wish I hadn't...; I shouldn't have...

■ This shows regret for something done in the past.

■ The なければ is the negative (from ない) and conditional ければ’

■ The よかった is the past affirmative form of いい (good). Together, it conveys the idea of "It would have been good if" or "it would have been better if..."

Negative Conditional form of a verb + よかった

How to make the negative conditional form:

-る Verbs

■ Drop the -る and add -なければよかった

To eat: 食(た)べる　→　食(た)べなければよかった (I wish I had not eaten)

-う VERBS

■ Change the final -う sound to the corresponding -あ sound, and add -なければ. In the following example, the word ends in "mu". Therefore it becomes "ma":

To drink: 飲(の)む　→　飲(の)まなければよかった (I wish I had not drank)

■ Note, with verbs ending in う itself, change it to わ:

To buy: 買(か)う　→　買(か)わなければよかった (I wish I had not bought)

IRREGULAR VERBS

■ する (to do) ➟　しなければよかった (I wish I had not done)

■ くる (to come) ➟　こなければよかった (I wish I had not come)

■ I wish I hadn't...; I shouldn't have...

■ This shows regret for something done in the past.

■ The なきゃ is the casual negative (from ない) conditional

■ The よかった is the past affirmative form of いい (good). Together, it conveys the idea of "It would have been good if" or "it would have been better if..."

Shortened Negative Conditional form of a verb + よかった (Casual form)

How to make the casual negative conditional form:

Basically, construct the verb as you would with なければ but replace the ければ with きゃ.

-る Verbs

■ Drop the -る and add -なきゃ

To eat: 食(た)べる　→　食(た)べなきゃよかった (I wish I had not eaten)

-う VERBS

■ Change the final -う sound to the corresponding -あ sound, and add -なければ. In the following example, you change "mu" to "ma" (just as you did with the ～なければよかった)

To drink: 飲(の)む　→　飲(の)まなきゃよかった (I wish I had not drunk)

■ Note, with verbs ending in う itself, change it to わ:

To buy: 買(か)う　→　買(か)わなけきゃよかった (I wish I had not bought)

IRREGULAR VERBS

■ する (to do) ➟　しなければよかった (I wish I had not done)

■ くる (to come) ➟　こなければよかった (I wish I had not come)