When we feel we have been treated unjustly, the best we can do is confront the injustice and talk it out with the people concerned.
Take notes. Contemporaneous notes are crucial if the injustice is of a legal/professional nature.
Not dealing with an injustice often means we allow it to build up in our mind. We imagine the worst case scenarios . Everything becomes magnified. And we find bitterness creeping in. The best cure for bitterness is to prevent it entering in the first place. When it takes hold we need to go back to the drawing board. Forgive the person who treated you unjustly for a start. Holding on and replaying the situation in our imagination will solve nothing. On the contrary, it will add to the resentment and increase the bitterness.
Writing is therapeutic.
Tears can bring healing.
Gambling masks many things and solves nothing.