While I was trying ways to ward off recurrent thoughts, I hit upon this elegant method to do it. I do not know if the method is portable to other minds, but here it is:
Use the recurrent thought as a marker or a breakpoint for recollection of how you arrived at it, and what started it. Essentially it amounts to remembering your stream of consciousness backward. This reveals the potential branching points in the stream, that lead you to the recurrent thought. Over time, you can avoid the branching points because you know where it leads.
At least in my mind, the stream of consciousness runs through a landscape designed by a “force”, an unconscious desire to reach a final cause, a telos. Often the telos is some unresolved decision with a potentially disastrous expected value for a single decision or lack thereof. And the something unconscious is reading the stream of thoughts much like I am becoming aware of it. This unconscious part of me nudges me from thought to thought to the unresolved decision it wants me to look at.
Keep in mind that this method has only been tried situations in which my unconscious is unsatisfied with my conscious assessment of the decision I made. But I guess that cannot be avoided. There are situations in which all decisions have a permanent taste of dissatisfaction to it.
I have a disclaimer though: I do not know if by pushing these unresolved issues into my own Jungian shadow I might create compensatory behaviors in dreams and so on. But I am working on it.