I had a cat years ago that was one of "those" losses. Took me a long time to get over. If this helps any, try to focus on the good memories, not on the sadness of loosing him.
Treat yourself nice, I'm sure that you made sure he had a excellent life with lots of love.
RE: Is a mentally ill person potentially a dangerous person and a treat to society ??
Here is a idea, round us all up and send us to a asylum. Thats how they used to do it back in the day.