The hard thing is not understanding the concepts but learning what this implies for your coding style, especially when you come from a garbage collected language like Python.
Both concept can at times give you hard to solve tasks, but it usually is because the problem you are trying to solve is hard and you cannot just naively hack away without thinking long and hard about it.
Other than that I learned liking the borrow checker and lifetimes because you will get a incredible narrow scope of which variables can matter when — which makes debugging much easier
