Newswatcher, thanks for a very personal answer.
Also there is satisfaction in uncovering any of the many links in a causal chain, even when you don't get them all.
At least you have the pride in recommending corrective actions that will lead to improved safety against some future risk. I've always figured that my contributions over my career have saved one planeload of 747 passengers. That's enough motivation for me.
I've never heard the word depressing used by any of my compatriots.