No matter how justified you are in your negative emotion, you are still messing up your future.
The fact that you are focusing your attention on your negative feelings means that you are inviting more negativity into your life, and it WILL mess up your future.
"What we think we become" Buddha
You may think that you have every right to be angry about things that have happened to you, and you are probably right. Yet, who is it hurting for you to continue nurturing all that negativity? You cannot change what has happened and you certainly can't change the way others think or what they do. The only person's mind you can or need to change is yours.
Anything that you are holding on to, any anger, resentment, revenge, any negativity, is eating you up and creating stress that can manifest into illness.
Don't spend the rest of your life harbouring defeatist feelings over things you cannot change. Give yourself the solace of deleting negativity from your thoughts completely and fill yourself up with joy and happiness instead.
"Create the highest, grandest vision possible for your life, because you become what you believe." Oprah