I tried this when I was learning Go; I just took a few hours (if that) to write really low-level code by hand, instead of doing what I usually do and copy / paste code from somewhere else and edit it. It helped me memorize basics like creating a slice or map and things like that, and improved my confidence in the language by a lot in a short amount of time.

I should do that more often with whatever I work with. However, my current job is so random (lots of odd jobs left right and center in between ad-hoc meetings and interruptions) I have no need for it.