When people worry, doubt extensively or experience a lot of uncertainty, they become increasingly focused inward, thus of what is going on with them internally. All the problems become ruminations, as it were, while the solutions are getting further way.
A practical way to deal with this is to redirect the antennae more outwards. This exercise comes originally from the world of the theatre.
Actively walk around the room or you can do this outside as well and name out loud what you see. For example; "tree, water, grass, flower". By putting the perception from the inside outwards, you come into a more active energy.
A walk or bike ride can also work wonders. Physical activity releases substances in our bodies that improve our mood. Furthermore, physical exertion helps to break down stress hormones. That's why running is often recommended when you're feeling sad. Try this and see what works for you.
Source: "The Spirited Body" by Rene Diekstra.