We use to clean a place that as an independent living apartment complex. I developed a good rapport with the maintenance guys they would unlock the units for us. Most of the time they were completely empty and we were cleaning the carpet before they were renting again. One time we were going in to clean an occupied unit, one that I've done before. The man that lived there was uh.... interesting. Very heavyset man who would lay in the middle of his living and watch pornos (I guess he would carry on even with the maintenance men in there doing work), the carpet was always severely matted and stiff there.

This man also had a "lady friend" that would come to visit from time to time, I found this out about the first time we cleaned his place. I was training a new guy, and of course I get routed this guy's place. The maintenance guys let us in and I walked in first and found the guy naked and dead in the middle of the living room. The maintenance guys always got a chuckle of having to deal with him and I could hear them snickering in the hallway, but when I came back out bug eyed, they knew something was wrong. First time they've found someone dead there, and the apartment complex wasn't going to pay to have it "properly" taken care of so I pointed the maintenance guys in the right direction.
Richard is correct that they affect you years down the road.
Last and final trauma type clean up I ever did and will do is - my little cousin Terry and I found my cousin Joe hanging in his closet. His knees were bent and barely 2 inches from the ground. I remember holding/supporting him while Terry found scissors to cut him down. Joe was a big boy, mostly solid muscle but pushing 260 lbs and was a star lineman for our football team in his day, and a year younger than me. This was in 2007, I was 20 at the time - actually March 4th, 2007 so hes been gone 7 years now. Took all I had to not have him fall on top of me. Tried CPR while Terry called 911 but I knew he was already gone because he his body evacuated itself. I don't know why I felt compelled to do it but after the police did their investigation, they said we could get someone to clean it up. I went to home depot and bought bags, tyveks, masks, razor blades, etc and gutted the closet that night. Could pay me a million bucks and I still won't ever touch another trauma clean up ever again.
The company I worked for in Utah(2009-2010) wanted to start this type of work Me being the only one with experience in it they wanted me to train and head that division up. I got rather emotional when we were talking about it as a group and had to share that story with my co-workers. I ended writing protocols and training manuals but never set foot on a job site. I am thankful I had a very empathetic and compassionate boss who was very understanding of my situation. I've met some people who aren't.