Solo 20-Mile Success...Which Is Weird

This long run can best be summarized by the email I sent to my friend Brett shortly after finishing it. Brett is a Boston expat (now living out west) and accomplished marathoner who also has the good fortune of being my upcoming roomie at CIM. We've been keeping each other abreast of our recent training, by which I mean commiserating about how out of shape we feel and how frustrated we are that things aren't going as smoothly as we'd hoped. But recently we both seem to have rounded a metaphorical corner, an unexpected phenomenon no better exemplified than by my strangely awesome solo long run on Monday afternoon.

"So, as I mentioned in our text convo, I've had a surprising recent development: I'm not feeling like total shit. My workout Saturday was solid, for starters. Then I was supposed to do 20 but I pushed it because my legs were tired Sunday, then crazy bad weather here Monday morning, so I finally got out and did it this afternoon/evening (snuck out of work...shhhh...) One of my biggest weaknesses from this training cycle is I haven't done enough long (18+) runs, so I was a little uncertain about how this one would go, especially solo and in the afternoon which is weird timing. But I felt GREAT. I'm not sure about pace because I don't run with a Garmin but it wasn't slow. And literally afterward I stopped, clicked my watch, and said 'Welp, that was easy.'
What's going on????!!!"