To be wronged is nothing, unless you continue to remember it. --Confucius
One way that I use to deal with a situation wherein I've been wronged in some way is to remind myself that the action (or inaction) is about the other person, not about me. I strive to not take it personally, knowing that the action would have happened to whomever was present in the situation, myself or any one else. This often helps me to let it go.
Another reminder I use is that I don't know what the person who wronged me is going through at the moment. There are myriad difficulties in life, and sometimes we just end up being targets due to simple proximity.
It takes thought control, a lifelong practice, to divert our attention from a wrong and move on. We give the wrong action power when we continue to remember it. Confucius' quote is another way of saying the common phrase, "forgive and forget."