Only when it's gone do you wish you'd done more to protect it.

只有当它消失的时候，你才会希望你做了更多的事情来保护它。

youdao

Maybe you only know it when it's gone.

可能失去了你才能体会到。

youdao

When love comes, flowers bloom. When it's gone, wind blows them away.

爱情来时花开遍，爱情去时风吹散。

youdao

In the presence of this ligand, this molecule, it's open, it allows transport of this ion, when the ligand is gone it doesn't.

配体存在的情况下通道才打开,允许这些离子穿过,配体离开后,这些离子就不能通过了

耶鲁公开课 - 生物医学工程探索课程节选

Even better, when you remove it, it's gone.

CNN: module

And they thought they had taken the lead after 10 minutes when Blackstock's header looked as though it may have gone in despite the efforts of Dean Kiely.

BBC: QPR 0-2 West Brom

The decision was widely applauded as a rare example of the stewards using their common sense - a bit of which would have gone down well when it came to discussing Hamilton's misdemeanour.

BBC: The right ruling on Hamilton?