How is “this is it” used?

In Mud (2012), one line is: “This is it. This is it.”

Which movie is “this is it” from?

The clip at the top of this page is from Mud (2012).

This is it. This is it.

8 作品で登場 · 1 本目

イディオム

the expected event is just going to happen

326 本の映画に登場

1
the expected event is just going to happen
Well, this is it! Wish me luck.
2
this is the main point
'You're doing too much.''Well, this is it. I can't cope with any more work.'

定義：Oxford Advanced Learner's Dictionary 第 9 版