Yes, not only am I a Marathon Maniac by membership in the club but truly in mentality. I run a lot. It seems like I'm always training for yet another marathon, even in these COVID times. Granted, I don't approach the mileage that the elites put in for their training, but I hit as much as 60 miles in a week right before tapering in a normal cycle.
It's to be expected at times that the motivation just flies out the window. Yesterday was just such a day -- I had absolutely ZERO motivation to go out the door and run. And my lack of energy merely augmented that lack of motivation. This is where the trust comes into the equation: trust your mind and body. Listen to what it is telling you. Sometimes you just need to pull back a little bit and give yourself a rest. It's ok. That's also where the forgiveness comes into play.
So you took a day off that wasn't part of your original plan. Take a look at what you have coming up in the next several days and see whether it makes sense to add that missed mileage back in across those days. Or do a run a little bit faster to make up for it. Be willing to adjust your schedule if it makes sense.
Today was a fantastic run. I did 13.1 miles on the treadmill in 1:38:48. Very pleased with the run, because it was VERY comfortable. I certainly would have been able to keep that pace for a full marathon if I were inclined to do my virtual MCM today rather than next weekend. And that is very encouraging for pushing it faster (in the 3:05 - 3:10 range) for my December race.
The above notwithstanding, if you wind up getting into a rut of multiple days of low energy/zero motivation and choose not to run or otherwise workout, you need to examine what else is happening. Are you eating poorly? Are you not getting enough sleep? Too much stress at work? You may need to force yourself to go for a run -- even an easy pace for a few miles -- to break you out of that rut and get back to your previously normal routine. Being willing to trust, forgive, and adjust isn't intended to give a way to completely give up.