Here is what Jeremy Stafford (author) says on Page 15 of the 2016 Guns And Ammo "Personal Defense" issue of their magazine:
"If you have the legal means to carry a gun and choose not to then you are a coward and a fool. Harsh words, but it is the truth."
I understand the "fool" part. By not carrying (and training and practicing) you are making yourself subservient to street thugs, robbers, rapists (if female), and last but not least although unlikeliest -- armed terrorists.
I don't agree with his "coward" part however because not everyone is cut out for a gunfight. A gunfight is simply a fight that also includes a gun. You need to be in good physical shape, jog, box, kickbox, shoot, get professional training, practice on your own, be alert and vigilant and always aware of your surroundings. You also need a fighter's attitude, not a wimp's.
That's why not everyone is cut out for it. And if you are not cut out for it then you should not carry at all, because ultimately your gun is then mostly likely to be taken from you and used against you.
The world is full of sheeple, wolves, and sheep dogs. So it all depends on which you are and whether you are willing to work hard to become instead.