Depression.
No one prepares you for the emotional waves you're about to be hit with.
The waves of deep sadness hitting you with everything in them.
Sometimes it's not just the waves of sadness that hit you.
It's also what's caught within them that hits.
Baggage
Anger
Loss of Appetite
Irritability
etc.
Now, when you're hit with those waves, you don't just come out sopping wet from the tears.
You come out scraped and bruised from the fight you were giving while being trapped beneath,  just trying to break the surface to gasp for air.