If you want to do endless miles, then just go do it. Today I did make it out of bed at a reasonable 6:30 and started walking at 7:50. I had no goal really. I just filled my hydro-pak with water and started walking in Meador Park.
I went 17 miles. When to stop?
The idea of miles is positively addicting for me.
I had 2 phrases from A Course in Miracles Chapter 6 in my mind: Alignment with light is unlimited. Allow no darkness in my mind. Over and over, realizing when I was thinking darkness and limits.
After about 3 hours, I had an enlightening moment. See, my mind had been roaming around the United States thinking of long distance races I want to do. Or just thinking of multi-days. Or thinking of how hard it is to do the miles without any sort of race or reward; just do the miles, write it in your book and go on. My left foot was slowly but surely getting sore.
Then after one of my phrase repetitions, it hit me: my mind IS unlimited!! That is IT! Yes, a crucial part of ACIM learned: I am not a body I am free. I am still as God created me. I get to choose all my thoughts. Nothing I see means anything. I think I can, I think I can, I think I can....the little runner who could.