Some lessons are priceless...

Never trust GPS in forested area surrounded by colossal mountains of the West Coast.
Pre-crash:
Before putting video goggles, I always do a short flight, testing behaviour of the aircraft. Then I switch to "loiter", put goggles on and get comfortable.
This time I put the quad in loiter, put the goggles on (takes 5 seconds), and then watch the video feed showing the quad is drifting sideways.
Too late.