This might not be helpful to you, but I'm finding that the same method works for learning non-native languages as well:

When I had to learn grammar rules, I just went with what sounded right and it was always correct. The rules were rarely applicable in real life, and most people don't even use or learn them. Therefore, it was more helpful to just read books and passively learn the "rules" than to try to do rote learning or to actively learn proper/formal grammar.