A key problem that I only realized after having recently returned to Haskell after a long absence is that our expectations about learning new programming languages and/or platforms set us up for failure. For example, I generally eat new programming languages for breakfast (or bedtime reading, really).

But I've noticed that Haskell isn't like picking up the PL flavor-of-the-week. Instead, it feels much more like learning a new area of mathematics. It's common with a novel area of math to just have to bang your head on it for a while. If you hang on through that phase, the cognitive switch flips and then you wonder how it was ever difficult. So it goes with a language that feels much closer to math reified, and for which most of the patterns we're used to from our imperative platform experiences just don't apply.

One good piece of advice I've seen a few places is to work through the U. Penn CIS 194 lectures and homeworks[1]. The lecture notes refer to other good resources for reading, including chapters of http://learnyouahaskell.com/ and more. But the real winner is just taking the time to just work through the homework problems. It's annoying at times. "Hey, (don't/shouldn't?) I know this stuff already?" But you'll probably get stuck at places, and those places pinpoint precisely the missing foundation blocks you'll need to reason successfully about your Haskell programs. Stick it out, but don't be afraid to search the web for help if you get too stuck. We self-taught types don't get office hours to keep us pointed in the right direction.

[1] This term in particular gets referenced: http://www.seas.upenn.edu/~cis194/spring13/lectures.html