> What's the quintessential "now I get it" experience, in your mind?

Learning that https://calva.io/paredit/ exists and moving your cursor along the AST or moving expressions around with nice hotkeys. Then making simple macros for infix notation and SQL and so on, which operate on the AST too. Realizing that there is no "architecture" because any repeated code or pattern can be easily abstracted away with a macro. Realizing that you can just describe your problem on paper, making up the perfect notation, then implement that notation in a few hours.