How do I stop the cycle of worry which leads to paralyzing anxiety and high blood pressure?

The cycle of anxiety and worry can be frustrating. 

Worried thoughts and thinking the worst often stem from avoidance and the uncertainties caused by this avoidance.  Confronting your avoidance triggers can help alleviate the anxiety that you feel.  For example, if driving in a car seems to exacerbate your anxiety, it is not the driving which may be causing the anxiety, but the avoidant behaviors associated with this.  Identifying avoidance triggers and challenging these through gradual exposure can be a helpful strategy to alleviating anxious and worried thoughts. 

If worried thoughts are related to relationship issues, the same principle can apply in identifying issues of avoidance, then gradually challenging this through one-on-one confrontation and open, direct communication. 

In addition, anxious and worried thoughts are exacerbated by uncertainties, which are inherent in life.  By identifying and focusing on what you can control in any given situation, instead of what you can't, you can alleviate some of the anxiety and worry related to coping with uncertainties. 

On a spiritual/existential level, anxiety and worry can often stem from mistrust in life, as well as mistrust in oneself.  It can be hard to recognize how life can be inherently striving to grow, to actualize one's potentials, to be developing in the best possible outcome.  It can be hard to feel hope and trust in yourself, in life itself, and to see a cumulative design with one's life's experiences.  Deepening this trust can come with time, the aging process, and deepening wisdom.  Taking some time to consider this perspective, how past painful and difficult experiences have enabled one to grow, develop purpose and meaning, can be a helpful exercise to gaining trust in life.  There is a saying that "a good physician cures illness with medicine, and a great physician cures illness with poison."  Ask yourself what are the ways you have changed poison into medicine in your life, used adversity to develop unique strengths and capacities?  Deepening your hope, patience, and trust that the best possible outcome will happen in your life, although maybe not the outcome logically that you expect and want, is crucial to feeling absolute freedom from worry.