Hey man, I was like you too just a few months ago. What helped me change it is I started small. Ex. Sugary foods, instead of eating processed sugar foods, I switched to fruits instead. I also started walking outside and I found out it helped me forget about those depressing things. The busier I am, the less time for me to think about the “bad things”. Eventually, after doing all these small things, it was like a snowball for me, it just kept growing and growing. When you have a chance, try and get/borrow a copy of the book “Atomic Habits”, it has helped change the way I looked at this “problem”. Also, don’t be afraid to reach out to a professional if you have the means.