I dont know about where you are located (western Europe) but here in america coping tools like stress balls, comfort toys, blankets, pillows.....basically what ever object helps the person to cope with their problems is a welcome thing and is even a therapy approach. many treatment providers supply their clients with something to hold, cuddle squeeze or use in other ways before during and after therapy. even inpatient care people are allowed to have their stress balls, stuffed animals, pillows, blankets and what have you as long as it doesnt contain any parts that can be used to cause harm to one self or others (ie sharp points knives, drugs or alcohol)

yes I have my comfort tools I have 4 stress balls in 4 different strengths/resistance levels, 8 stuffed animals, 10 scented candles, 3 blankets, and a room full of other crafts that I do in the hard times. when I was inpatient we were taken on a sort of field trip to a mental health workshop where make your own coping tool (teddy bear, stress ball, stress sand filled object...) each of us came back to the mental ward with that coping tool we had made to use at any time even during therapy sessions.

that said when I first read the title for your post I expected it to be something triggering like keeping an object, clothing, from a crime scene like keeping the soiled clothing from being abused. is that what you meant, keeping something that reminded you of an abuse or painful event you went through?

if so in that case my answer is no I never kept anything that reminded me of the pain I went through during abuse that would have reminded me over and over again that I was abused. I used a completely different tool which was to dissociate, which effectively caused me to forget/wall off what happened to me into alternate personalities (DID), that way I could continue on with my life with out having to remember what I had gone through.