This is the hardest module in the curriculum. Full stop.
The borrow checker will make you feel stupid. You are not stupid. Ownership is genuinely a new way of thinking about memory that most programmers have never encountered. Years of Ruby means years of never thinking about who owns a piece of data, when it gets freed, or whether two parts of your code are aliasing the same memory. Rust forces you to think about all of it, all the time, from day one.
The Rust Programming Language ("The Book") is one of the best language books ever written. But it still cannot make ownership easy. It can only make it learnable. Chapter 4 -- the ownership chapter -- will take you 3x longer than any other chapter. That is normal. Everyone struggles here. Senior engineers with 20 years of C++ struggle here. The difference is they struggle with unlearning old habits; you will struggle with learning new concepts. Yours is actually the easier path.
Here is the emotional curve, and I am telling you this so you do not quit at stage 3: excitement (week 1, "this is cool") -> frustration (week 2, "why won't this compile") -> despair (week 3, "maybe I'm not cut out for this") -> breakthrough (week 4, "oh, THAT's what the compiler is telling me") -> love (week 5+, "I finally get it and it's beautiful").
The payoff is real and it extends beyond Rust. After understanding ownership, you will understand memory management in every language you touch. You will know why Ruby has GC pauses and what triggers them. You will know why Go's GC is simpler but makes different tradeoffs. You will know why C has buffer overflows and why they are not just "bugs" but a fundamental design flaw. This module rewires how you think about data.
One honest warning: do not skip the exercises to read ahead. Ownership is not something you can understand by reading. You understand it by fighting the compiler, losing, reading the error message, and trying again. The compiler errors are actually excellent -- Rust has the best error messages of any compiled language. Trust them.
You already know how to ship Rails apps. This module teaches you what is happening underneath.