Having a vivid imagination is a good thing. Directing that mental energy into worrying about negative thing though, is potentially detrimental to a persons health.
Often we can direct huge amounts of mental energy into worrying about situations that may never eventuate. This worry has an impact on health as it activates the stress response pathway of fight or flight; putting you into a survival state. When your nervous system is forced into this survival state your repair mechanisms are stopped, immune system is compromised, you become more sensitive to pain and creative thinking is lost.
Worrying is not problem solving. This may be better handled with relaxation, meditation, a walk in nature and even getting a chiropractic adjustment. All of these have been shown to help bring balance back to the nervous system.
Learning to foster a great imagination may allow you to come up with innovative ideas and solutions to problems but allowing it to be stolen for the use of worry has the potential to rob you of your health and these creative solutions that could benefit your future.