So, I stuck with this "Controlled Immersion" method.
Instead of studying the rules of grammar in a book, I paid close attention to how grammar was being used in context.
I decided to focus on the 4 or 5 most important grammar points in Italian - the "core grammar" - and to learn that well, rather than try to learn every single grammar point in the language.
Each time a particular verb tense, preposition, or irregular verb appeared, I noticed it, and thought about why it was being used in that situation.
If I got confused by a particular grammar point - which did happen - I would quickly look up the basic rules in my book.
I wouldn't try to memorise the rule.
Or even practise it.
I just wanted to be aware of what I was missing.
And then, every day like clockwork, I would come right back to my "Controlled Immersion", until, eventually, I'd seen that grammar point so often, it had started to become normal.
Within the space of just a few weeks, a huge transformation started to take place.
I stopped translating in my head, and as viewers pointed out on YouTube, I had begun to internalise Italian grammar.