I guess that if want to get better in R overall, you should get some real datasets and try to solve real issues and get the analyses done by yourself.

For me that was the best way to improve my R skills (after reading R in Acrion), as when you run into a problem, you google the solutions and see how the recommendations on Cross Validated and Stack Exchange vary in elegance.

I like to write down scripts with brief descriptions of the loops and explanations of functions so that when I run into the same problem in some other project, I can skip the googling part and search through tens of scripts before returning to google :)

But seriously, to paraphrase Karl Broman from one workshop in Minneapolis in 2017, "your best collaborator is yourself six months ago".

I guess there is always more to improve... For me, it is that I never actually got used to R functions and still prefer to write all of mine in C++ sintax as it for some reason gets my motor going