When you blame others for your troubles, you give them control of your life. Free yourself from your own anger, from your own resentment, and you'll find vastly more room for serenity and abundance.
It's bad enough if someone has wronged you in the past. Is it of any value for you to continue suffering from it?
Your best strategy is not to prolong the pain, or expand upon it. Your best strategy is to get past it as quickly as possible.
Whether or not anyone deserves your forgiveness is not the point. The point is, you deserve to forgive, to take back control of your life, so that you can live abundantly.
Your forgiveness may not even make a difference to those you forgive, if they're even aware of it. For you, it makes all the difference in the world.
When it is you who is feeling the hurt, it is also you who can heal the hurt. Heal the hurt, and move past the pain, with FORGIVENESS.