When I get into a cycle of worry, I find it helpful to consider what I can do. If I can take action to alleviate the worry, then the worry is worthwhile. If I cannot take action to alleviate it, then it is not just a waste of energy, but harmful negative energy. In those instances I think it is useful to work on changing my mindset.
This is a concept described by Gay Hendricks in his book The Big Leap. I think it is useful in our everyday lives, but perhaps particularly poignant today.