I did Dark Retreats twice in Nepal, once in China and once in Russia - these were completely isolated, with no possibilities of disturbance.
The rule of the silent retreat, that my teacher taught me - requires a full reset if there is a transgression.
For my own retreats at home, which are shorter duration, I generally go up to a friend’s vineyard in my area which is pretty isolated, and turn off my phone. I establish a sacred space and invoke 10 guardian deities in each direction. Once that happens, no one will want to come around, not even bugs strangely! Over time and millions of recitations later, the presence of guardians has gotten stronger! Its like no one wants to come miles within that area or even think or call me. A specific guardian deity named Tiraskarini is evoked, and Her main job is to cloak you from physical and other dimensional beings. She needs to be evoked once every 24-hours, but she does an astounding job!
Initially, though I was “blocked” from outside, there were urges from within to call home, check on family, worry about work, etc. I had to resist the thoughts, resist the fear that something had gone wrong, etc. And over a period of time, I have come to entrust myself, at least those 3-days, to a higher power, and believe me, it is very liberating! Not being in control of yourself, having to worry about yourself, feels very freeing! I don’t worry at all and generally find that when I return, things are already mysteriously taken care of!
