I'll never lose heart even if I should fail ten times.

即使失败10次，我也不灰心。

《新英汉大辞典》

If I should fail I would try again.

万一失败，我还要试一试。

youdao

If I should fail, I will try again.

万一我失败，我会再试。

youdao

Should you fail to stop killing those babies, I think you should be punished for killing babies."

如果你不停止杀婴儿，你就会因为杀婴儿受到惩罚”

耶鲁公开课 - 心理学导论课程节选

Technically, I should fail out on the screener since I have worked for market research organizations, do such research myself from time to time, and definitely know how to game the system.

FORBES: Everybody Wants To Survey Me

"In the event that this should fail, I have already begun to lobby the leaders of other political parties in parliament, to refer the law directly to the Constitutional Court, " the DA's parliamentary leader Lindiwe Mazibuko said in a speech before the vote.

BBC: South Africa 'secrecy bill' approved by parliament

For the record, I am someone who believes that drugs should only be used when other modes of treatment fail.

FORBES: Why David Healy Is Wrong About the Safety of New Medicines