at it

见at

that's it

that is the main point or difficulty

那正是要点；那正是问题所在

‘Is she going?’ ‘That's just it—she can't make up her mind.’.

“她去吗？”“那正是问题所在——她拿不定主意。”。

that is enough or the end

够了；好了

okay, that's it, you've cried long enough.

好了，你已经哭得够久的了。

this is it

the expected event is about to happen

（盼望的事情）即将发生；即将来临

this is it—the big sale.

快了——就要大甩卖了。

this is enough or the end

够了；好了

this is it, I'm going.

好了，我就要走了。

this is the main point or difficulty

这正是要点；这正是问题所在