The old joke is that youth is wasted on the young. I don’t think that’s quite true, but it is true that when you are young you just can’t fully appreciate how well your body works. Run three miles, ride a century on a bicycle, take a multi-day backpacking trip, no problem. If you get a little sore or stiff, you’ll feel better tomorrow.
I probably felt that way into my 40s. But sometime about 10 years ago, it got harder. Recovery was slower. If I wanted to maintain my weight, I had to do more aerobics and eat less. I started to notice injuries lingering.
The latest injury is to my elbow. Tendonitis. I’ve been, in no particular order, swinging a hammer, splitting truckloads of firewood, practicing bokken and jo katas, and working out three evenings a week at the dojo. Along with using it for daily life. So now it’s ibuprofen and ice, using the left side more, and favoring it hoping it will calm down.