It is not realistic that grief over a lost marriage should be worked out in a month or even several months.
Most people will continue to deal with the emotional ramifications of loss for many months, sometimes even several years.
The dialog between numb and upset continues over time as the person emotionally digests the nature of the loss.
Ultimately, enough time passes that the loss comes to be thought of as something that happened in the past, and that is not a part of day-to-day life.
There can be fear at the prospect of being single again, possibly for a long time (or even forever), and with having to cope with changed financial, living and social circumstances.
There can be anger at a partner's stubborn obstinacy and pettiness, abuse, or outright betrayal.
Different coping strategies and skills are appropriate to address each of these aspects of divorce.
Someone whose marriage was betrayed might take a longer time to work out their grief and to do it in a more vocal way than someone who chose to leave a marriage of their own accord.
Someone who found out suddenly about their spouses' affair might grieve differently than someone who has watched their marriage deteriorate for years.
Grief doesn't so much go away as it becomes irrelevant after a while. Most of the time it is best to allow yourself to grieve in the ways that come naturally to you, at least part of the time.
Eventually life comes back to 'normal' and the intensity of loss retreats.
Any and all of these emotions are enough to make people miserable, and to find them wanting to cry at 3am in the morning.