Confidence Is Fragile

My dog Nestle had pretty much given up on the world when I adopted him from a shelter. He quickly bloomed to appreciate the good things in life - walks, meals, treats, even training. But it took a full six months for us to establish a bond, and he still spent too much time with his ears pulled back and his mouth in a tight grimace. We cautiously saw new sights, met new people and dogs, practiced agility purely for the increased confidence, and he blossomed. People who see him out and about with me think he's a perfectly sound dog. But I know differently, and that was brought home to me recently.
I had some quite serious medical problems, and through November and December, we had several occasions when we all (dogs and humans) got in the car, drove to the emergency room, and I went in and didn't come back out. This has resulted in Nestle being very anxious when left in the car. He started out just hiding and trembling on the floor in the front (the dogs ride in the back and aren't supposed to come into the front. Then he tore up some Christmas presents that were on the floor in the front. Since then he has torn up other things on the floor.
So his confidence is, as I always knew, fragile. We are working on getting his comfort level back, taking car rides and leaving the car for only short periods at a time. He has had several good days where he remained in the back, and another episode of tearing up a bag of pastries in the front. It is especially bad if I have to go to the hospital for tests or the cancer treatment center for appointments. He obviously recognizes these places.
But we are working on it, and I'm sure he will settle down again in time. It just reminds me that living with dogs is a constant work in progress.