The title quote is from Seneca. I grew up with a different phrase, but it still worked for me: “80% of the sh*t we spend time worrying about never happen anyways” ~Herbert “Sharpless” Spencer
And it’s not that these guys were fearless. Rather, they broke down those fears, those worries, those paralyzing doubts and categorized them in bite sized pieces. My grandfather was a rifleman in WW-I; life expectancy in the trench wasn’t too good. But he survived to marry, to have and to raise twelve kids, to send some to college, and to comb the hair of his grandchildren… which numbered like  by the time he passed away.
This was his system for dealing with worry and anxiety:
Name each fear that keeps you up in explicit terms: he began with a piece of paper describing the action that he feared taking—it could be starting a new company (his was a coal mine, hardly a start up as we think of one today), asking for a raise, ending a relationship, death, destruction, betrayal, etc.
Then he would add three columns:
In the first column- titled “HOW BAD”, he would outline each worst case scenario in terrific specifics. And he would easily have 20 or more here. Being specific was key, he added gruesome details and tried to scare himself.
In the DEFEND column, he would write exactly for each bullet point what to do to prevent the worst case scenario from happening. Sometimes, the answer was “do nothing and wait”, which was a thing.
In the FIX IT column, he would note how to get back on his feet if the worst case scenario came to pass. Who would you need to talk to? What skills or help would you need? Has someone less smart figured this out?
What is important is that a lot of times we are fearing a temporary setback; (on a scale of 0-10, what could this mean…a 3 or 4?). In the grand arc of life and living, this isn’t really so bad. Now, consider trading that 4 risk in exchange for perhaps a 8 or 9 benefit… now that’s a bet you want to take!
Fears are imaginary unless and until they are realized, whereupon they become reality. Meanwhile, use the Sharpless Method to quantify your fear.