Image credit from Hecate, here.
Since we are runners--and not just any old runners, we cover vast distances that "normal" people cannot fathom--this image is somewhat relevant.
Now, I'm not talking about literally shooting yourself in the foot. I'm talking about figuratively doing so. As in failing to hydrate properly, or not carrying enough calories along on a long run. Or not dressing properly for the worst weather that you are likely to encounter. Or getting off course...you get the idea.
Most horror stories of unpleasant backcountry running experiences deal with lack of preparation or planning. Everyone gets complacent at times, gets casual about checking and double-checking your gear and your plans, and AHA! You run into a problem that woulda/coulda/shoulda been avoided entirely.
When that happens, you, my friend, have shot yourself in the foot.