I've also experienced similar failures. I've tried to learn Haskell several times, and every time I meet the Monad section in the tutorial I lost my concentration. One of my friends who is proficient in Haskell told me to just start coding without trying to understand the advanced concepts, but I wasn't inclined to do that as Monads were hanging over my head, and I really wanted to understand what they are before writing some piece of code.

Funnily enough, things were changed after I learned Rust. (I know I'm saying like a Rust zealot, but it's true!) After using Rust's `Option` type, and realizing its `.map()` and `.and_then()` are similar to `fmap` and `>>=` in Haskell, I finally began to grasp what functors and monads are. And that led me to understand the "implementation details" of Haskell. Before that, I thought `seq` was purely written in Haskell. But it wasn't. It is basically a compiler magic, and GHC specializes `seq` to allow eager evaluation. The same thing goes with the IO type; the monad itself has nothing to do with making I/O be done. I/O is possible solely thanks to the implementation details of the IO type, which resides in GHC. Plus, I can also guess that that part of GHC is probably not written in Haskell, because it is not possible to make side effects in "real" Haskell.

So, Rust was my admirable Haskell teacher. (Thanks, Mozilla!) It's like a stepping stone between the imperative world and the functional world. The funny thing again is, after having fun with Rust for months, now I have less reasons to go back to learn Haskell... Rust is already too powerful, performant, and easy to understand, so Haskell feels less appealing to me. Haskell had been enviable to me in the past, but now it isn't anymore, (un)fortunately.