Mastering Rust

Hello all! I feel like I've gotten pretty good at the basics / intermediate bits of rust. I understand (simple) lifetimes, traits, newtype patterns, basic async, don't struggle with the borrow checker anymore, what I think is enough to understand all/most application-level code, and have written a few personal tools and apps.

However, I still feel like I haven't truly mastered rust. Looking into library code of complicated projects scare me, I don't understand macros, unsafe is another can of worms, i only have a tenuous grip on lifetimes, etc. How can I know I've really understood everything?