The human body is a truly miraculous thing. I continue to be amazed at how mine steps up to the plate and improves as I push it.
Case in point: yesterday I did my first day of this 7/3 rotation for my run/walk routine (note the transposition in the order from what I usually say...deliberate to reflect that I really do run a lot more than I walk now). Like most "first days" of a newer, harder schedule, my body felt it. When I got home and it was time to climb the stairs, I had to get off and walk the hall between almost every single floor, cuz my knees and back were screaming for mercy and I was WIPED OUT.
This morning I did it again. It's only morning 2 of this rotation. When I came home I was able to climb clear to the 4th floor before needing to walk the hall a bit.
Amazing, adaptable, incredible, miraculous body. That's plenty of reason to be grateful!