It is one of the strongest things in existence, yet it is considered disdainful by the majority of the world and certainly by American culture. Those who practice it are often ridiculed and subject to sneers. I grant that forgiveness, while a force to be reckoned with, can be extremely difficult to execute. One of the things that makes it such a difficult practice is that it requires humility. It is an impossibility to forgive and simultaneously believe that you are better than the one you are forgiving. Forgiveness requires rejection of the prevailing mantra of humanity: "I'm number one." Those whose first task is not self advancement are not only strangers to this world, but offensive to it. The world will reject that which is not its own, and forgiveness is certainly not its child. Even other "liberated" Christians may chide you for demonstrating forgiveness -- especially if the other person "doesn't deserve it." External pressure can be difficult to deal with, but internal resistance is positioned to wreak even more havoc on good intentions.
As a Believer you may know that we should forgive as Christ did, you may have heard beautiful stories of redemption (in addition to your own), and you may very well stand in awe of those who faithfully practice such generosity. However, admiring the quality in others and weaving it into the cloth of your own life are very different. Again, the pain of forgiveness stems from pride. People don't want to be humble. Not one of us, in our flesh, finds humility or submission enjoyable. They are in direct opposition to our very nature. Because of this, forgiveness is not something we can carry out on our own. The first battle is to make the decision that we want to forgive. Sometimes it just feels better to sit on our self-righteous fannies and feel justified. I have had to remind my self many times of Romans 12:19 "Beloved, never avenge yourselves, but leave it to the wrath of God, for it is written, 'Vengeance is mine, I will repay, says the Lord.'" Justice is not my business. As much as I would sometimes like to take the position, I am not meant to be the punisher of all who wrong me. I have to frequently remind myself that I am thankful the Lord has taken on that burden for me. Can you imagine how our lives would be if the only justice was that which we could implement on our own? Stressful much?
After the decision that we want to forgive has been made, we have to administer it. In my life there have been times I have wanted to forgive, but have simply found myself incapable. It just wasn't in me. Instead I have cried in my spirit "Father, help me to forgive. I can't do it." That is the beginning of true forgiveness. "I can't, but You can. Help me." It is only by the power of the Spirit and his abundant life in us that we can find the strength required to truly, openly, completely forgive. This is extremely different from the say-you're-sorry-and-hug-each-other brand of forgiveness kindergarten totes. Forgiveness is a matter of the heart. It is about our attitude not "being nice." Outward show without inward change is fraud of the heart.
The last, and possibly the most difficult minefield to cross is that of hurt. If no one was hurt forgiveness wouldn't be necessary in the first place. To say "I forgive you" is to also say "You caused me pain." Sometimes, especially when an apology isn't offered from the offending party, anger is the only thing to testify to the unfairness of what occurred. We are tempted to hold onto it because it is the only thing that says "This happened and it isn't okay." Secondly, forgiveness means that we have to release the other person from the burden of healing us. In our hearts we want to withhold forgiveness until we feel okay again, until there is emotional restitution. It is difficult to realize that it is an impossibility. As much as an apology might help and a repentant attitude is a salve, nothing another person can do will fully heal us. The sooner we relieve others of the responsibility of our emotional states and take our hurts to the only one who can actually cure us, the sooner we will experience the fullness and the goodness and the freedom of forgiveness.