I had to learn to live in my today.
Like you there was a nonstop dialogue playing in my head. I would face each day with a "just for today" conviction.
Expectations only led to more disappointment and heartache.
I commend you for putting your children's welfare first, maybe for today, just live it the best you can, tomorrow is going to take care of itself.
Both of my grandfathers lost their wives in childbirth, combined they raised 31 children alone, thru the depression. When times are tough for me I always remember that others have endured before me. You can do this. Believe in you. Your kids already do, and that is what matters most.
Sending you tons of support.