Target practice soothes my nerves. I switch from full auto to single shot mode and it makes me centered and focused.
Age will make a difference but When you hit fourty look out.
Focus on something good, don't dwell on bad. Remember, you can't change the past, so why let it control you
You can't and probably shouldn't try to make feelings go away. We can control our actions, but not our feelings.
But we can talk back to negative stuff. If, for instance, we are remembering something cruel a person said or did, we can talk back to them in our heads in such a way that we feel better, We can talk back to our past tormentors or betrayers. Making fun of them is the best way to confront them. In other words, we can ridicule them, make fun of what they did or said. Humor can distance us from bad memories and feelings.
If that doesn't work, remind yourself how lucky you are not to be experiencing the bad memory right now. Remember how strong you have become from adversities you have gotten through. Praise yourself for having survived the situation. Ridicule those who gave you a hard time.
There are also some physical remedies for a sudden case of the blues. Take a long hot shower, then a cold shower, then go for a half hour brisk walk. Then listen to a comedy album or a Mrs. Miller album. Or read Dave Barry.