First, learn how to fall. There are suggestions from reputable online sources like
https://www.health.harvard.edu/staying-healthy/how-to-fall-without-injury#:~:text=Keep%20your%20knees%20bent%20and,are%20lower%20to%20the%20ground. I've long cycled on rough trails and run and walked in the dark on rough trails, usually with large hounds running by me. So, I've fallen a lot and have learned, I guess from experience, that I have lots of time from the moment that I know that I'm going to fall to the point of impact to rearrange my head (first) and body (second), to direct away from large rocks and trees, and sometimes even to condemn myself or a dog for causing the fall. A lack of panic certainly helps!

Second, it might help your diagnosis to differentiate between lightheadedness, which may be produced by vasodilation, and dizziness, which may involve a vestibular issue. So try to recall after a fall if you felt either a blind closing over your eyes or a spinning, if either!

Good luck.

Peace.