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(The forgiveness I am trying to analyse below is about serious matters, such as serious personal offense, crimes, and any type of abuses within relationships, it dose not include the tolerance/forgiveness of differences in ideas, wrong doings of general level.)
The content of "forgiveness" consists of two parts: 1, a peaceful state of mind that has transcended the painful/unfair past; 2, a willingness of re-building relationship with offenders.
The former is prerequisite of the latter, but it dose not necessarily lead to the latter.
Forgiveness is CONDITIONAL: 1, it requires victims emotional strength (transcending the past - recovery from damages and regain self esteem); 2, offenders' efforts to earn forgiveness*.
Forgiveness without both of these conditions is irrational, unreal and will not survive long.
When someone is abundantly loving, forgiveness can be a "charity". However, if someone practices this "charity" of "forgiveness" completely aimlessly or unconditionally, he/she is no more than a rich person showing off his/her wealth by giving out money away unnecessarily. In other words, this "charity" will not do any good, except functioning as a decoration of our personal strength.
I think unforgiveness usually has two reasons: victims' insufficiency of emotional strength; 2, offenders' lack of effort to earn forgiveness.
The unforgiveness caused by both or either of these reasons is totally reasonable, and worth our sympathy. As outsider, we should not encourage victims to "forgive" their offenders just for the sake of "forgiveness", because it is natural for a person to moan when he/she is suffering, and it is natural for us to defend ourselves when we are under attack. In other words, when any type of unfair conflicts happened and produced damages to one sides, victims' right should be always our the first concern.