Definition
This phrase is used to express that someone's misfortune is their own fault.
活该倒霉（自作自受）
You didn't back up your files, and now that your computer crashed and you lost everything, that's your hard luck.
你没有备份文件，现在电脑崩溃，你失去了一切，那是你自找的。
He didn't follow the traffic rules, and as a result, he got into a car accident. That's his hard luck.
他没有遵守交通规则，结果出了车祸，那是他自找的。
If you choose not to study, and then you fail your exams, that's your hard luck.
如果你选择不学习，然后考试不及格，那是你自找的。