When I'm within sight of a 5K finish line and my lungs are on fire, there's always a few more drops of gas to be found to power me on home.
When I've busted through the wall on a marathon and my legs are screaming bloody murder, it's still possible for the mind to tell the body what to do. Not easy, but possible.
Yet when I'm barely breaking a sweat but my HR is too high, no amount of mental toughness can get the heart to beat any slower than it wants to. It just doesn't work that way. Invoking every cuss word I know doesn't work either. Feels like it should work, but has quite the opposite effect on the heart. Dammit.
After 7 consecutive weeks of steadily decreasing average mile pace (12:21, 12:03, 11:40, 11:28, 11:26, 11:10, 11:02), my 2 runs this week were back at 11:30 pace - why, I have no clue. It's like my heart forgot how to run. I'm going to blow this week off and start again next week.