There are too many people in this world, and life is too short, to hold on to any one of them who you can't forgive. If one out of the x-billion or so people roaming this silly planet at any given moment disappoints you so severely that you can't forgive, dispose and move on to the next. It doesn't make sense to remain non-forgiving in order to protect yourself from being hurt as much again by someone, just as it doesn't make sense to resent everyone else in your life for the hurt they have not yet brought to you but might. There is as much, and sometimes an even a greater, chance that any one of us could/would hurt you, as there is a chance that someone who's already hurt you will hurt you again.

One benefit of forgiving is being someone who people will not be afraid to approach or love... someone who seems capable of understanding, accepting, and/or loving in return. Why would anyone want or continue to be involved with someone who can't forgive?

To forgive, I suggest you take a step back and view the unforgiven objectively. Try to understand who the person is and why he/she does what he/she does. Whether you succeed or fail to understand, you have a choice to accept who they are or not. If you choose to accept, because you wish to continue to interact with the person, or for whatever other reason(s), then forgiveness should come more easily... because the benefits of forgiving will become clear enough to drive the forgiveness. If you choose not to accept, it's unwise to keep the person in your life at the same level they were at which allows them to hurt you to the degree that you can't forgive. It's not good for the person, it's not good for you. Demote him/her, or somehow put him/her at at distance from which they can't hurt you in the same way again.

Now I have a headache.