What about some simple katas? I’ve been learning a few new languages and don’t want to forget the syntax / common methods, so I pick an easy kata and solve it in each. I find that this is usually enough to prevent me from forgetting everything
Grokking Algorithms and A Common Sense Guide to Data Structures and Algorithms
Something I’ve been trying to cultivate is the ability to “externalize” my thoughts (even if it’s just to myself). Like, more of a process-oriented approach. it’s so easy to bang out some code that works, but sometimes I look back at what I wrote and think “how did I wind up here”