Rachinator, we have a saying around here that works well in times of high stress.
Just do the next right thing.
Don't worry about tomorrow, the surgery, the post-op, etc..... just take each minute as it comes & do the next right thing needed at that moment. Instead of looking at the whole line of dominos set up waiting to tumble, deal with each, one step at a time.
I remember "getting" this concept while RAH was in jail for DUI & I couldn't/wouldn't help him out. My world was absolute chaos & I had no clue where things were headed. I had gobs of worries over his safety, our finances, the future of our relationship, etc. but I went shopping instead because DD needed uniform pants for school because the weather had turned cool that same week. THAT was the next right thing for me to focus on at that moment. Everything else was out of my control. Shopping for pants made me realize she had outgrown her winter jacket & needed a replacement. When we finished that we were hungry so I worried about lunch. And on & on I went through that weekend spending time focused on each task in front of me instead of worrying about what I couldn't know. HTH!