Disclaimer -- I'm not a nurse. I have 33 years experience as a paramedic and an Emergency Physician. I, like a lot of my nursing colleagues, have seen hundreds of dreadful things during my career. From time to time throughout my career I have had intrusive thoughts -- where I just keep thinking about the distressing nature of a case even though I don't want to. What I always promised myself is that I would let intrusive thoughts last for a maximum of seven days. If I kept thinking about a case after 7 days, I promised myself that I would go and talk to a counselor about it. I don't know what the correct threshold is, but if you are still having intrusive thoughts after a week, you might want to think about visiting a counselor. It might save you a lot of grief or even your career.