Fighting to be right

I have been turned down for a refund of monies paid for substandard services. My concern is my overwhelming need to be heard and found right. The injustice and blatant lies the other party has told to our mediator are intolerable – in my opinion. These, of course are all my thoughts and emotions. Indulgent..yes. recognised..yes. ready to let them go..nooooo! I have had a few too many of these situations happening lately. Finding it hard to see the solution without giving in and losing a bucket load of cash. Seem to be always fighting to be right. Somehow I set myself up for these situations. How to stop? Appreciate your guidance.