When a situation is troubling me, and there is nothing or little I can do about it, once I have done what little I can, the job, whenever the situation occurs to me mentally, is to conceive of God's direction and strength flowing in the direction of the situation and the people in it and to visualise those people accessing that direction and strength.
This, I've found, is the perfect solution to all negative obsession. It's temporarily replaced by positive obsession, but the positive obsession is so repetitive and boring that the mind eventually finds something else to occupy itself with, and I'm free.