I'll answer, Skidmark. After mulling it a bit I am going to try to explain how I got from "there" to today...
About 8 years ago CC had recently passed in MO and I survived the cancer that killed my little brother and nearly killed one of my best friends. We had some crime issues in my neck of the woods and I decided that I wasn't going to now be taken out by some criminal. I bought a modern semi-auto appropriate for carry and signed up for the next CC class I could which was a few months away.
I went to the range and carried at home, in the car (legal here) and in my offices. I carried condition 3 getting use to the idea of carrying and got some range time. I started thinking through scenarios of actually using my sidearm for self-defense. At first it was more about the tactics of using it - practicing draws, dry fire exercises, etc. But over the weeks it started being more about would I use it. I started thinking about that a lot and Clint Eastwood's line from Unforgiven kept coming to mind, "It's a helluva thing to kill a man. Take away everything he has and everything he's ever gonna have," or something close to that.
I took the CC class and immediately signed up for more advanced courses. At some point I decided that yes, I was willing to take a life to save a life. It wasn't a quick decision and it wasn't any one thing that cinched it. At some point I had to make a decision - either I was going to be willing to use lethal force in which case I would carry daily or I wasn't, in which case there was no point in carrying. I looked at the world, my responsibilities in it to my family and employees, and decided that I am willing to use lethal force to defend myself and those I care about.
All in all it was a decision I thought about for maybe 3 months with a sidearm nearby reminding me of the reality of the thing. Since I decided, I have not regretted nor had reason to question it. Certainly there are details of it that have come up that have required further examination, such as in the thread about hesitating to use lethal force for self-defense if the bad guy were a child.
Eight years of daily carry later and I still think of that movie line and I still hope I never have to make that decision, however, I am as at peace about it as I think I can be having never had to face the realities of that decision.