I have been in that dark place and I sympathize. I can tell you that my life began to turn around when I began to simply pray for God to provide for my needs - and believe that He would. Ever since then, when I begin to slip into the old pattern of worry, I remind myself to give it to Him because He can bear these burdens and I can't.
If you do not believe in God, perhaps you believe in "The Secret" which tells us to focus upon that which we wish to attract to ourselves. You want life to be better for your children and grandchildren, so perhaps writing about what your hopes and dreams for them are might help.
Remember that old song? "Accentuate the positive, eliminate the negative, latch on to the affirmative, don't mess with Mr. in-between." If you have nothing else to focus on that is positive, let your love for your family sustain you. Please don't give up. Never give up.