Here and there you read that it would be a good idea to film* your golf swing in a period when you are playing well to have it as a reference.
That’s a good idea, but that alone is not enough.
If you fall into a bad patch, film that swing and compare the two. Then you can find out what’s wrong.
When you make the films, get a face-on view and a down-the-line view OF THE SAME SWING. That means you will need to have two cameras rolling at the same time from those two viewpoints.
I did that once and discovered a bad habit of getting too steep in the backswing, which had the effect of jamming my right arm into the shoulder, which closed closing the clubface.
Films compared, problem solved.
* I’m a product of the film and wet darkroom generation, so I just keep using that word.