Forgiveness is a topic that often arises in counseling.  Many people feel
like forgiveness has to be achieved for them to move on. 
Forgiveness as defined by the Oxford English Dictionary online as
“Stop feeling angry or resentful towards (someone) for an offence, flaw, or mistake
No longer feel angry about or wish to punish (an offence, flaw, or mistake).”
This definition states that forgiveness is releasing anger.  It is not accepting the act that happened, nor is it reconciling with the person who caused the hurt.
Forgiveness Expert Fred Luskin gives these steps to forgiveness
  1. Acknowledge the harm the event has done to you
  2. Experience the feelings associated with the event
  3. Talk to someone else about the event
    [1]
Many people struggle with the first step.  Clients often tell me that they are over something, simply because it happened many years before. As if just because something happened 20 years ago it no longer mattered.   You can’t experience the feelings associated with the event until you have acknowledged the harm that you have experienced.  Often it is the desire to avoid experiencing those feelings that causes people to deny the harm that has been caused them. 
It is important to remember that forgiveness is a process that includes resolving grief.  It is not something that comes easy or quickly.  Forgiveness can be further complicated if the person whom you wish to forgive is still in your life but acts differently now.  An example of this is an abusive parent who is now elderly and treats you differently.  I find that people often get stuck at that point.  The relationship is different now so why dredge up old memories?  The problem with that philosophy is the memories are there whether you are dealing with them or not.  Unresolved grief has a way of causing depression or anxiety if it is not addressed. 
“When you hold resentment toward another, you are bound to that person or condition by an emotional link that is stronger than steel. Forgiveness is the only way to dissolve that link and get free.”

Catherine Ponder
For more information on how to forgive Mr. Luskin has a more detailed article which discusses nine steps to forgiveness.

[1] What is Forgiveness?  By Fred Luskin August 19, 2010 http://greatergood.berkeley.edu/article/item/what_is_forgiveness/