How do you know when you're working through a concern versus just feeding it?

I'm trying to understand a pattern in myself and would appreciate some outside perspective. Whenever something important is happening in my relationship or future, I tend to think about it a lot. Part of me sees this as being responsible because I want to make thoughtful decisions and avoid preventable mistakes. The problem is that I can never quite tell when that process stops being helpful. I'll start by thinking through a legitimate concern, but after a while I don't know whether I'm actually solving anything anymore or just repeatedly revisiting the same issue from different angles. The confusing part is that in the moment it still feels productive.

It's only later that I realize I may have spent hours mentally working on something without getting any closer to an answer. For people who have struggled with overthinking, anxiety, or decision-making in relationships, how do you personally tell the difference between healthy reflection and getting stuck in your own head?

TL;DR: I tend to think deeply about relationship and life decisions, but I can't always tell when I'm productively working through a concern versus just mentally spinning my wheels. Looking for advice from people who have dealt with something similar.