You mention not wanting a "cure all" but just support. I'd like to offer you my hypothesis that this is part of your problem. You should be looking for a cure, not a palliative. And there is a cure, but it is a difficult one (and not without its rewards).
What's the cure? Others have mentioned meditation, and I second that. Meditation acts as a kind of "off" button for incessant thoughts that trigger each other. By letting concrete reality totally consume your awareness for even one instant, you squeeze out the self-reflective consciousness that is a key part of that loop, and weaken it. (Your body is a key part of this loop at two points: first as a source of "concrete reality" sensations, and second as a kind of residue of emotional reaction.)
Success on this path requires the ability to sit still and not get up even if you think of something better to do, or because you are bored, or because your butt hurts, or because you're anxious.