Blame it on age! Since I'm older than you, at 70 3/4; and, not as fast as you, or as I used to be - age makes sense.......
Since I started riding again, with a bad knee that will have to be replaced someday (if I live long enuf) I have come down with diabetes, 4 stents in my heart, and a host of other physical problems ---- I've been doing a lot of calculating.............. Yep. it's age!
I remember when I used to be faster, ------- I think. And I still love the ride along the river!