Going over it is not working on it

This is worth separating carefully, because people defend rumination as being responsible.

Problem solving has an end. You reach a decision, or you find there is nothing to decide, and you stop. Rumination has no end. It circles, it changes the wording, and it hands you back to the beginning.

The useful test is not what you are thinking about. It is whether the thinking terminates in something you then do.