When can I say “make it”?

Hi, I know this is kind of a stupid sounded question, but I can’t be sure when I can say, “make it.”

For instance, is it OK to say “make it” in the contexts like:

A) I’m gonna have an audition tomorrow, and I hope I gonna make it.

B) I am involved with a project. It’s very hard and has many obstacles, but I think we can make it.

I used to use “make it” without paying much attention to the “it”, thinking “it’s just an idiom that is close to the meaning of ”succeed”, but one day a friend of mine asked to me, “what is ‘it’?”.

The examples A and B sound acceptable to you? And if so, what exactly these “it” mean?

Thanks!

-M