Someone I love suffers tremendous anxiety. I wonder sometimes if a person with that temperament can help themselves from worrying all the time.
When I am stressed or anxious or worried, I try to employ some of the strategies suggested by the Anxiety and Depression Association of America. They have a number of good suggestions at https://www.adaa.org/tips-manage-anxiety-and-stress.
The best for me is to find the humour in even the blackest of situations. Laughing at your troubles, even the most overwhelming of predicaments, I find very therapeutic. Being able to laugh heartily no matter how bad it is helps. I believe nurses employ gallows humour to help them deal with the overwhelming nature of their jobs. I try to do the same.
I also find just taking the time to breathe deeply and just relax your body is of assistance in calming me. My breathing can completely change my physical response to whatever I am feeling and permits me to calm my mind.
Finally, I find the Serenity prayer written by Reinhold Niebuhr very wise.