I’ll give you some anecdotes from my own history.
I’ll be 50 in late April this year, so it sounds like I’m a bit older than you. Been training martial arts since age 13, and have had an interest in fitness since before that, running and strength training. As an adult, training has been my mainstay and my passion, and I would often spend somewhere near 20 hours a week training, in addition to having a job and a marriage. Training three times in a day, and sessions lasting as long as four hours at a time, were common.
In my early forties I became a parent, and suddenly my time and energy did not belong to me anymore. Over a period of about four years my training dwindled to almost non-existent and I fell out of shape.
Now my son is old enough that he doesn’t need all of my time, and for the last three or so years I have been working to get my training back. For a couple years I was very hit-and-miss, and that start and stop has been difficult. With Covid I lost my employment and I’ve had time to focus on my training again and have finally regained some real consistency. I still have interruptions at times, sometimes even for a couple weeks, but mostly my consistency is good.
I don’t have a bad next day, but I find that after I train, I need a nap. I often sleep through the family evening movie, before going to bed. I think a lot of it has to do with my age, slowing metabolism. Improvement comes more slowly than it did when I was younger and I lose it more quickly if I lapse. But the consistency seems to be really important. I can endure it more easily when I don’t miss sessions.
Another thing I wanted to point out was making sure you have been checked for any health issues. My younger brother has always been an athlete, having competed at State level in high school cross-country, track, and swimming. He maintained a very active lifestyle as an adult. In recent years as a parent, he fell out of shape, and was working to correct that. But he couldn’t seem to make any progress in his running. He was consulting with his doctor, was about to have a stress test but had to postpone because his blood pressure was really high. Then he had a heart-attack at age 44, about a year and a half ago. He survived it, woke in the middle of the night and realized what was happening and got to the emergency room. If he hadn’t woke up when he did, he wouldn’t have woke up again.
So this is just one example, but get your health checked to be sure you don’t have something lurking in the background.