Yep, working those bad ones is tough. I was scared for myself when the time would come that I'd have to work a bad one. Amazingly I did fine on scene. You got the adrenalin going and know you got a job to do, and tying to hurry and get traffic flowing as fast as you can or at least another lane open if it's not shut down waiting on the ME, but all is well.
Then it's when you're all done you climb up in the truck start rolling away from the scene and soon thereafter it hits you, WTF did I just clean up and all those thoughts go thru your head, I wonder if they had kids, how old were they, does their spouse know yet, then you want to call your own kids and family to make sure they're OK and remind them to drive safe. Then you back to the yard are set it down and get a good look at it and realize how fugged up it really was, and it does stick to your mind for a few days.
The ones I really like, are the ones where the car is crushed up like a beer can when you roll up on it and think Oh ****, this is bad, and driver walks up and says can you help me get my garage door opener off the visor and my laptop bag out of the back seat. Cars are friggin demolished but the people are all walking around.