I don't think the concepts are hard to understand, I think that - in Haskell - they're just being presented in a way that is incompatible with my way of thinking.
Having found Haskell materials as simply not suited for me I decided - quite a few years back - to learn Haskell (or the concepts behind Haskell, at least) my own way: by learning first Erlang (it sounded cool), then Scheme (mainly to be able to read many, many papers that use it), then OCaml and Scala (because the type systems and pragmatism) and finally Clean (to fill the last gaps in my knowledge). I progressed from dynamic to static typing and from eager to non-eager evaluation. It took me I think about 2 years to do all this and, of course, it wasn't that easy, but somewhat surprisingly it worked. I never wrote - and I'm not sure I ever will, but that's a completely different matter - any non-trivial Haskell code, yet I'm able to read and enjoy Haskell-related papers.
It's important to realise that there is always more than one way to learn things. You should know yourself well enough to see when the "normal" way simply isn't for you; this way you can go search for alternative ways. I guarantee that you'll find them, if you search hard enough :)
Having found Haskell materials as simply not suited for me I decided - quite a few years back - to learn Haskell (or the concepts behind Haskell, at least) my own way: by learning first Erlang (it sounded cool), then Scheme (mainly to be able to read many, many papers that use it), then OCaml and Scala (because the type systems and pragmatism) and finally Clean (to fill the last gaps in my knowledge). I progressed from dynamic to static typing and from eager to non-eager evaluation. It took me I think about 2 years to do all this and, of course, it wasn't that easy, but somewhat surprisingly it worked. I never wrote - and I'm not sure I ever will, but that's a completely different matter - any non-trivial Haskell code, yet I'm able to read and enjoy Haskell-related papers.
It's important to realise that there is always more than one way to learn things. You should know yourself well enough to see when the "normal" way simply isn't for you; this way you can go search for alternative ways. I guarantee that you'll find them, if you search hard enough :)