I'm not sure there is a definition of "going dim." If going dark is no contact with your S, going dim is just a little less than no contact. Going NC or dark is usually done to protect the person going dark. Early on it helps you get your feet under you, gain strength and get in control of emotions to be able to respond instead of react.
The very real difference in going dim and detachment is, we should be lovingly detached in all our R. The opposite of detached is enmeshed or codependent, which are not healthy, being detached is healthy.
Hope that helps.
Me 57/H 58 M36 S 2.5yrs R 12/13
Let me give up the need to know why things happen as they do. I will never know and constant wondering is constant suffering. Caroline Myss
