Learn git branching
Understanding Git branching has mattered a lot in my career, and it is genuinely hard to picture what a rebase does to a commit graph from the command line alone.
This solves that. Interactive exercises with a live diagram of the commit tree - you run a real command, you watch the branches move.
It covers rebasing, cherry-picking, detached HEAD and remote tracking, which are exactly the parts people fake their way through. And you can undo anything, so there is nothing to be afraid of breaking.
Best thing I know for making Git stop being a set of memorised incantations.
See also: