your story reminds me of why riding horses can be so exciting and dangerous.
Horses too make split second decisions that might make sense to them at the time (like not wanting to step into a scary 1 foot diameter puddle) but can endanger your life.

It's hard to make split sec. decisions always, and i think i would have veered in front of the truck too, then beat myself up for it for the next 3 weeks.
be glad it turned out okay!