The most destructive habit I've ever had is the habit of "Thinking". For decades I tried to "think" myself to sleep at night and the result was disastrous. I grew up thinking that if I were clever enough, if I thought hard and fast enough that I could escape whatever it was that I wanted to get away from. I mistaking thought I could think my way out of whatever I found displeasing. I found out in my forties that "thinking" is it's own kind of prison. To have thoughts you can't turn off is quite frankly torture. The things that are unpleasant or disruptive on the outside of me are far less frustrating that what goes on inside my head and in my thoughts.
The the key to freedom from my thoughts is to find a way to live in the present moment. When I am in this moment I have everything I need and I have no need to be "Clever". The past no longer exist and the future takes care of itself when I exist in my own breath of being. Anxiety only exist when I am trying to exist in the future. There is no anxiety when I am in the moment, just a mindful state of being. Stress lets me know I am not in the moment.
The the biology of stress is an interesting issue, anxiety causes inflammation. Inflammation causes disease. That is how we make ourselves sick with worry and stress. Worry's cumulative effect over time is disease causing.
The kicker about giving away our moment to worry is, no matter how hard or how good we worry, we can't change the outcome or consequences of events we stress over. We have given away all the possibility of peace because we choose to future trip rather than LIVE the moment we are breathing in.