Everything is OK until something goes wrong.
When off road riding, especially when we are alone, we should really consider our safety and minimise risk as much as possible.
Wearing a cycle helmet is a must, and body armour is becoming increasingly more common, even for xc riders.
Leaving your route with a responsible person and maybe regular contact with them, should also be seriously considered.
Carrying ID is better than nothing. However, wearing ID with any details of any medical problems is even better. Take a look at this article, in which I recommend the helmet type ID -