Mercury's Oriental Accidental Debility but Why?

1
If you pay attention you'll notice that people begin to do "stupid" things when Mercury is retro, crossing a Node or Combust. The more of those the bigger the "stupidity". Add in a Filling Moon and Heh ?

It is also clear that Mercury Oriental is pessimistic or fearful, and Occidental optimistic and courageous.

All in the first paragraph I can explain as problematic but NOT this Oriental phase.

Any opinions as to why it is problematic?

H