Change every negative thought into a positive one.
I believe that being negative on one issue starts a spiral effect on many other negative thoughts.
First is to acknowledge the issue.
Second is to find positive situations from the issue. As a divorce, with me, it was a very positive step for me into a new life, a new journey.
Third is to catch the negative thought as it happens an change the thought , replace with a positive thought.
At first it feels like- wow I sure had a lot of negative thoughts- but soon they are replaced with positive thoughts.
Not only are thoughts negative but friends and family thoughts are sometimes also negative. For me, I did a grand detox of friends, family etc , some friends I had known for 20 years but realized the impact of negativity that they had on me. It is a trade off.
There are many books, from the library, on setting boundaries.
Be positive on all of your thoughts.