How do I tell what actually causes what, not just what correlates?

Finding correlations is a real skill, so start by owning that. Moving from correlation to cause feels like a wall, but it is a wall everyone in this field has had to climb. It is not beyond you. It is simply the next thing to learn, and it takes a different way of thinking than spotting patterns does. The heart of it is a single stubborn question: could something else explain this. When two things move together, cause is only one reason. Maybe a third thing drives both. Maybe the order runs the other way. Real causal thinking is the discipline of ruling out those other stories before you believe the simple one. Start practicing on your next finding. Before you call it cause, force yourself to name at least two other explanations for the same pattern and think about how you would test them. You will not master this overnight, but that habit of doubting the obvious is exactly the skill that separates cause from coincidence. Build it one analysis at a time.