Why do I panic when my tutor switches from 'Bahasa Baku' to street Malay?

I’m a false beginner who aced the writing exercises in my course, but I completely freeze when my native tutor drops the formal 'Saya/Anda' and switches to the 'Aku/Kau' dynamic expected in daily social life. I feel like I'm wasting my lessons by just nodding along. What’s the best way to practice this transition so I don’t feel like I’m switching languages entirely?