Three days after buying my first off-road bike, I sprained my back. I was 2 month doing physio, unable to do anything but stare at my shiny new orange beauty. It was totally demoralizing. I never, never, never want to feel that way again.
If I can ride half as well as "Old Paul" when I'm his age, I'll be a happy man. That is my goal. Most injuries for trail riders are not caused by accidents but just from riding - sprains, tears, cramps, etc. The writing is on the wall. The "winner" of this sport is the person who rides the longest, and the only way is to perform regular bodily maintenance. I can't get motivated to just "stretch" by myself and I'm not sure that stretching alone would be enough.
I joined a gym that prioritizes "prehabilitation" (i.e. injury prevention). Most Yoga studios would also work but, again, I'm not overly motivated by Yoga. When I started, I was going to the gym 3 times per week for a total of three hours. I twas tough at first but it became easier. Eventually, I began to enjoy it so much that I started going more often. Now I'm going 5 times per week. I love it! Its the best hour of my day.