Postposition anxiety: how to stop overthinking 'ka/ki/ke' before I speak?

I consider myself a false beginner—I can read a bit of Urdu, but the moment I try to form a sentence in a conversation, I freeze up because I’m terrified of getting the postposition wrong. It’s like my brain shuts down trying to calculate the case of the noun before I even get the verb out. Any tips for practicing these under pressure so I can actually start having real conversations?