I would like to know what Henry's recovery technique is. Anyway,
thinking this over some more, I'm thinking that so long as I have good
airspeed near terrain, vertical or horizontal (which I have always
practiced), and (here's the new part for me):

I don't fly into the corner of L shaped terrain

Flying close to vertical or horizontal terrain is OK with airspeed and
being prepared to recover from an upset. There is a place to go. But
flying into the corner of L shaped terrain is not recoverable in an
upset, not matter what. There is no room to the side nor bellow. I'm
boxed in.

Perhaps looking back at glider accidents in the mountains, we can look
if the accidents occurred close to the corner of L shaped terrain.