I think another factor that figures in to the equation for me is that I simply miss my Mistress.
The article I referenced makes mention of the emotional side of the equation and how one can suddenly feel abandoned, depressed or unloved. For me, I feel such a strong connection with Her when we're in session that when it's over and I'm back home and hours away from her, I feel alone.

Bottom line is that it's a pretty crappy feeling but knowing and understanding what it is and that it's normal for some can help one muddle through it.