I'm someone who learned declarative after imperative. In my experience, there are two things to understand about any declarative language: what it expresses, and what it actually does on the machine. The latter is often considered an implementation detail, but - at least for the people with imperative programming experience - it's actually crucial to gaining full understanding.
I remember my final breakthrough in grokking Prolog was realizing that the engine hides a glorified DFS that walks a graph of concepts for you. Suddenly, all the reasoning and non-deterministic features wasn't mysterious anymore, and performance-related implications became clear. Similarly, for people who struggle with async, it's beneficial to understand that async means somebody hid an event loop from you.
I remember my final breakthrough in grokking Prolog was realizing that the engine hides a glorified DFS that walks a graph of concepts for you. Suddenly, all the reasoning and non-deterministic features wasn't mysterious anymore, and performance-related implications became clear. Similarly, for people who struggle with async, it's beneficial to understand that async means somebody hid an event loop from you.