I had done my best, but I still failed in the exam.

我已经尽力而为了，但我考试还是没及格。

youdao

I could try to take decisions by myself, but I had failed twice. I was still not sure if I had made the right decision.

我试图自己做决定，但两次遭到失败，我当时仍然不敢肯定我的决定是否正确。

youdao

Judy: Yes, I know, I think I tried all my efforts but still failed, I am stupid.

是的，我知道，我认为我尽力了，但还是失败了，我真笨。

youdao