In this revised preface, due to the gravity of the stress the OP is dealing with, I wholely recommend from personal experience to make the manager aware of the severity of the stress, but not to expect much from them. There are few workplaces and fewer managers that equipped to meangingfully contribute to someone's recover in OP situation. The workplace may have an adequate policy or tools, but likely not. The manager may have enough sense to give relevant, meaningful advice, but I doubt it. That isn't raw, cynical pessimism, that is experience.
In order to personally manage stress and emotional pain, there are three simple things that have often helped me:
Take on a physically demanding task or activity: destructive (ideally, not personally destructive), creative, or entertaining. Maybe it's splitting wood, cleaning the yard (and the neighbors yard), or painting a fence (or painting a mural on the fence). Maybe join an amatuer sports club like softball or basketball, or start cycling regularly.
I went the extra mile, and left a technical field to work in construction for several years. Now that the trauma is behind me, I am slowly finding my way back to a technical field. The opportunity I found in construction through the work and the common culture to build and demolish, be creative and efficient, and frank and brash was therapeutic. Plus, I am a little handier around the house.
For my brother, and many, many other people, the gym works great for this.
Leaving your job is hopefully a last resort, but no matter what, do what is right for you.
For all the ugliness and sadness around you, there will be beauty and happiness. Try to gain an appreciation for these things that are surrounding you that to this point perhaps take for granted. Keep in mind the cycle of life.
Family and very close friends. They are in part why you feel like you do, but it is also those same people whom you will mutually see through this rough spot. They will help you, and you will help them. The opportunity to reconnect with those who have drifted is right there to take advantage of. You need no other reason. With more than ten years difference in age between myself and my youngest brother, we were close, but not very close until after my own turmoil. If it wasn't for that turmoil, we may never have built that relationship.
Focus on purpose
Breath in, breath out.
God, grant me the serenity to accept the things I cannot change,
The courage to change the things I can,
And the wisdom to know the difference.
I really don't think this needs much explaination, but per the encouraging comments, let me suggest that while this seems like a greeting card, it is a good practice to put in place. Be literal about it. Actually do the breathing with a purpose.
Being anxious or fearful about what is to come, or regretful or angry about the past isn't going to have any effect on either. The story about the past is written, move on. Some of it's less than pleasant. Things happen. Things happen all the time, everywhere, and to many different people. The story about the future can change based on what you do now. So do now, whatever it is you can do. Be hopeful, but realistic. Take chances, but be practical.