Sorry you're hurting but, you will see when you look thru these boards that you are not alone, there is help available and, there will come a better day.
What has put you in this state? If it's chonic disease, depression just seems to go hand in hand and the secret to an enjoyable day is having tools at our disposal to work thru the feelings.
My strongest suggestion is to seek a therapist, someone to talk with, to unload your anger, fear, disappointment on and come away with some insight in to how to cope.
There are support groups, meds, therapists.. different ways to deal with this and I urge you to seek out, as soon as possible, each avenue and make use of what is available.
I suffered terribly with depression because of my Ulcerative Colitis and the way it completely changed my normal, hopefull, happy, healthy life. I was robbed, as far as I was concerned, of the life I knew and, it would never be cured.
After two years of therapy, I can at least deal with my feelings and not let them rule me.
Also, add exercise (any exercise) to your daily program. That introduces endorphines into the system and makes us feel better.
And, live IN each moment and appreciate it for what it is, whether with the kids or your wife, a movie, whatever it might be. Concentrate on what you are doing, not your hurt, and it will help you begin to cherish and look forward to those moments.
Good luck and begin tomorrow looking for professional support. You are going to have days ahead that things will be better. There is hope.