I believe this may be what's called Catastrophic thinking. There are a number of ways to approach this - I use CBT worksheets to deconstruct my fears and force myself to think more realistically regarding the most likely scenarios as opposed to worrying over worst case outcomes. A quick Google search for "Decatastrophizing Worksheets" will give you access to several.

I take out these worksheets in advance of undertaking the action or event causing me Anxiety. I truly find it helpful. Examples for me are successfully combatting my own fear of driving, walking in public, and doing my groceries to name but a few.

I know this is excruciating. Good luck.