It's not fair that I have to try harder to run better

Apparently you also need to put in more effort 

Today's run (street): 4.1 miles
Yesterday's run (street): 3.2 miles

Considering how much I run, I'm not really that good at it. People tell me that I need to run more intervals, do more hill, core and strength training, run longer distances and run more frequently. I'll concede that those things could help, but they all require more time and/or the acceptance of more discomfort. I'm not a physiologist, but I've always understood that if you do something a lot, you get better at it. If I'm putting in a dozen or more running miles a week, shouldn't I see continuous improvement?

My running experience since late summer has been positive. I reduced my intake of sugar and simple carbs and that led to some weight loss. Running with less weight would usually yield direct improvement, but it wasn't until my friend KWL surprised me with a Garmin 35 watch that I started to see gains. That's because I was paying closer attention to my running data, especially heart rate. Using percent of HR max as a guide to pacing myself on runs helped me improve my average pace by almost two minutes a mile.

While I did see a measurable improvement from that, I've still been averaging 30-40 seconds a mile slower than my average pace from a few years ago. I know some of that is due to getting older, but it hasn't been that long since my overall performance began to noticeably drop. Of all the helpful suggestions people have made to me, the point about running frequency probably hits closest to home.

This morning seemed like a perfect running day and I expected to run as well as I did on Friday when I exactly matched my current pace. But today felt much harder. When in doubt, I always look at the data. My average heart rate for my last two runs were exactly the same. Rate of effort was the same -- 76% of max with the last six minutes pushing closer to 85%. Today's run also matched yesterday's for average cadence. The only variable was stride length, with Friday's being a foot longer than today's.

So if effort was the same, why was my stride so short? I did feel fatigued throughout run and that surprised me because I'd had a good night's sleep. There's really nothing that can explain why I did worse today (by 50 seconds per mile) except that every stride carried me 175 feet less every minute than yesterday.

I'm hoping that tomorrow I'll bounce back and open my stride enough to get back to current pacing. I know that some of my friend's suggestions for improvement would yield a quicker cadence which is the other lever I can pull to improve. But increasing cadence is tough and I still maintain that I should be getting faster because practice alone should be enough to make perfect.