Thanks for the write up, and hoping that you have speedy recovery.
YouTube is an invaluable place for advice about mtb riding and mtb skills.
You can do a lot worse that looking at this YouTube Channel.
https://www.youtube.com/user/mtbtips
This one is also very informative.
https://www.youtube.com/user/IMBIKEMAG/videos
This is another superb source of info.
http://www.mtbtips.com/beginner-mountain-biking-tips/#sthash.FYIxlgDB.iKpgDcjJ.dpbs
It has taken some finding, but buying a copy of this magazine style book is also well worth getting hold of.
https://www.buysubscriptions.com/special-editions/sports-masterclass-mbuk-mountain-bike-skills
Through rock climbing you will already have a good basis for risk assessment, and achievability, and you can apply the same mind set to your riding, and indeed you did, when you walked down the rock garden. It isn't about trying to be a hero.
When I was out last week, I was riding and thinking about just how far that my riding level had risen over the last two years, and started to think about how many levels of focus and decision making go into almost every metre of riding, all of which is carried out without even thinking about it.
It's another reason that I love riding in winter conditions so much, and tackling tight root strewn and rocky technical single track. From sub consciously looking at the colour of the mud ahead, and assessing before reaching it whether it is going to be firm or wet, to bouncing off the side of a wet root to set yourself up for a section 10 metres or so ahead, using the root to steer the bike, and following this by gauging speed that is required to get you past a particular stage or section.
I guess that coming from a trials riding background helps significantly helps with this.
Shame that you weren't in my neck of the woods, as I'd happily spend a day helping you along.
Ref the rock climbing. That used to be a past time of mine as well, and amongst other places, many happy hours were spent at Harrisons, High, and Bowls Rocks. I gave it a miss for while after there was a spat of belay ropes being cut whilst people were climbing, and I never got around to going back to it. I was never really that great at it, and was somehow never agile or smooth enough. It gave me a good foundation into my first career path as a tree surgeon though.