Curse of the Freaking Flashing Question Mark

Let's just say I got all cocky yesterday by thinking I could pull off a macOS High Sierra upgrade within minutes of leaving my office for the night, a decision that left me with the title of this blog post.  Yes, upon restarting my MacBook Pro after the failed upgrade, there it was:

A Big Fat Flashing Question Mark

So I got schooled today on how to recover from a botched last-minute-upgrade attempt and must share these words of wisdom to save you from the pain I experienced:

1. Back up your data, especially those treasured photos of your son's high school graduation and subsequent family vacation to Hawaii or risk losing those precious memories for the rest of your life.
2. Check your power settings and make sure your computer is NOT set to hibernate within the upgrade time frame, lest you end up with an inaccessible hard drive and a potential visit to the Apple store for resuscitation. (I came this close, but recovered on my own, thanks very much.)
3. Set aside a good chunk of time dedicated to the upgrade, because anything can happen and you really don't want to be staring at a freaking flashing question mark when all is said and done.  Like 4 hours - should be plenty.

​You are welcome.