You decide to leave when the ever-present question "what am I doing here?" gets answered somewhere in the back of your soul. With the answer comes clarity.
When I looked at my AH, all I could see was a bottle of vodka, so much so I nicknamed him "mr. smirnoff" - and still refer to him by that name. When our world came tumbling down, and the ship was sinking - I realized I had to jump or go down with it.
Just so you know, there is lots of help out there for us survivors.