I wish I only could find a light switch and turn off my personal stress.
The only way that I can really shield anyone if I am having a significantly difficult time is to "Detach with love", take care of my stuff, and then re-connect. It is very difficult to do, as I found out a few months ago when I told my sufferer I really could not see him because I knew I really couldn't contain my stress without projecting it all over the place.
I guess it depends on the situation, but I don't think there's a way to turn it off.
There's only honestly and communication with someone to let them know I'm not feeling my best emotionally and to try to get enough space to find my balance again.