I remember writing about first official releases of Clojure around 2010 when I was an editor at heise online Poland. At the same time I was coding libraries in Ruby and one thing was drawing my attention: lazy enumerators.
During works on I18n library with pattern interpolation in Ruby I had chosen to use lazily executed methods which could be stacked with the dot operator, giving nice processing pipelines. Around that time I was reading about Clojure and it hit me how much easier would this be in this language, with function composition and sequences, not mentioning the Delays or Futures.
I think Clojure was the first language I decided to learn before conding anything serious. It took me like 2 years to really give it a try, and leave Ruby world, so in 2013 I was making notes explaining how the basics work, and in 2014 started writing a tutorial in Polish called "Poczytaj mi Clojure" (which could be freely translated as "README Clojure" (README meaning both "Clojure, read to me" and "read me [some] Clojure". Through all 2015, during my sabatical, while sitting in a cafeteria almost every day, I coverd built-in special forms, functions, type systems, collections, sequences, macros and more, publishing it online.
In 2016 I started sharing first programs on Github. So I probably need about 2 more years to become advanced, according to "Teach Yourself Programming in Ten Years" – https://www.norvig.com/21-days.html
I remember trying Hydrox for documentation and so called literate programming approach, playing with function arguments and building macros changing positional args into named ones, using core.async and multimethods to build network bots, learning macros and protocols. I've made some free software libraries through the years, and I think I finally am able to build more complex systems.
Since I occasionally have a tendency to go into details too much, or to (re-)write things from scratch, I found Clojure to be the first language giving me enough power to finish those things in less than couple of weeks (1-2 months tops), and go back to a main project to continue. In other lanugages I tried for years I was kind of sinking into sub-projects (which needed to be taken care of) and hadn't enough energy to go back and resume works on more generic, systemic level.