Great question VDGS,
Nighttime when everyone is asleep and a fly can be heard buzzing in another room is when a fear can turn enormous for me. This is when I can pick up any one of Pema Chödrön's books to help "bring it back" to life size (and I do appreciate help in doing so).
Particularly:
The Places that Scare You: A Guide to Fearlessness in Difficult Times
There are also a few favorite quotes that have the effect of instant calm that I wrote on a mirror (I can share if you would like).
When a fear is running away, I try to put parameters around it by doing the best case scenario/worst case scenario exercise. Accept them both and be happy with anything in between. This is an exercise I need(ed) to do when I became responsible for the health and safety of a few truly helpless human beings (became a parent). It shocked me how the world suddenly became a place of exposed sharp corners. I had to get to the bottom of it in the best way I could so as to not spend the remainder of my days on red alert. Again, I read a book but then also talked with a therapist to gain a more global perspective on what was up.