Not sure if I can give you the answer you are looking for - I can give you the truth!
WHY ME? Mother was killed when I was about 3-4
FIRST STEP MOTHER was real diligent about severe child abuse for ten years (slamming head into cement wall, break broom handle across back, broke wood spoons over head, ONE OF THE BEATINGS: beat with a plastic hose so there were welts on bottom of feet, in hair on head, all over front and back of torso, arms, legs, and neck. - before her hose - she used a wire coat hanger stretched out to make a long oval, thrown down cellar stairs ... and other tidbits of attention
Dad, second step mother and 2 1/2 year old baby brother were killed on a Thanksgiving Day when I was 20.
MY ANSWER TO YOU:
1 - What to do when it makes you depressed?
Go jogging, walking, help pick up trash at a local park.
Notice what you are doing when you get depressed and stop getting caught in that type space.
2 - Often past memories of traumatic events resurface and trouble you.
When they resurface - it is usually is a point when your mind is idle and has nothing interesting to do - do some fun hobby and get it off your mind.
DO NOT resort to work - because too much work is not good for your ability to relate to others.
Personally - I have done things like start a Cameras Club, co ordinate a couple classic car shows, and am involved in the activities of a local facility which has an indigenous reptile exhibit when I spend time helping kids and adults experience live snakes so they don't panic and kill things which help keep rodents under control in the native ecosystem.
FIND A PASSION AND GET PASSIONATE - I own a classic car and a few snakes which are good ambassadors for fearful people to see up close and start toward allowing them to exist.
It is all UP TO YOU to stop letting it take up your time and fill that time with constructive things to do!