verb
grieve
GREEV/ɡriːv/
To feel or cause deep sorrow.
He grieves while holding the loved one's portrait beside an empty chair.
Etymology
The ancestor meaning “make heavy” also meant “cause grief,” connecting emotional pain with a burden. English grieve developed from causing distress to feeling sorrow or lamenting oneself.
In context
as you grieve you may find yourself sleeping too little or too much forgetting things or trapped in a brain fog these feelings are difficult but the acute pain doesn't last forever eventually the sadness begins to lift