My current outlook is shaped quite a bit by my experiences early in life. As many know, in my 20's I was an officer on a Navy submarine. We spent months cruising around hundreds of feet underwater, and we all knew that if we sprang a big enough leak we would die. But if we worried about that possibility constantly, we would go crazy.
So, what we did was take reasonable precautions -- operate according to regular checklists (such as rigging compartments for dive), conduct regular equipment inspections, ensure that people were properly trained to operate the boat and its equipment, and practice what we would do if we really ever did have a flooding casualty. Then, we went about our business without worrying.
If you have taken appropriate precautions and have a plan, you might start to worry when you start taking on water, but you should be busy enough trying to solve the problem that you are not incapacitated.
Translating to the present -- I have taken what I think are reasonable precautions to protect my portfolio in a variety of situations, and I have an action plan for reasonably foreseeable negative events. Worrying will not help me and may hinder rational thinking, so I don't. If and when things head south, I don't plan to be paralyzed by fear.