How do you know when you're processing a concern versus creating one?

I've noticed a pattern in myself that I'm trying to understand better. When something important is coming up in life, I tend to spend a lot of time thinking through different possibilities and outcomes. Part of me sees that as being responsible and prepared. But sometimes I wonder if I cross a line where I'm no longer solving problems and am actually creating stress about things that haven't happened.

The difficult part is that both "healthy preparation" and "overthinking" can feel very similar while you're in the middle of them. For people who have struggled with this, how do you tell the difference between thoughtfully working through a concern and mentally spiraling about something that may never become an issue?

TL;DR: I tend to think deeply about future situations and can't always tell when I'm being prepared versus when I'm overthinking. Looking for advice on how others distinguish between the two.