YOU SAID:

When you try so hard but you don't succeed...

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一生懸命頑張っても成功しないときは…

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If you do your best but do not succeed ...

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あなたがベストを尽くしたが成功しなかった場合は...

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If you did your best but did not succeed ...

INTO JAPANESE

最善を尽くしたが成功しなかった場合は...

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If you did your best but did not succeed ...