Resentment is blame. As long as I continue to blame the person, place or thing for my hurt, my resentment will remain unchanged and therefore, forgiveness will be impossible.
What has helped me let go of resentment in my life is the realization that I was not responsible, or to blame for the hurt that others caused me. Many victims, (this is especially true of abused children), will blame themselves for the actions of the perpetrators. They try to "figure out" why this other human being, often a person that they loved and trusted with their heart, and counted on to be of good will, behaved so unkindly towards them. They run the "if only" list in their heads over and over--"if only" I had done this, said this, been more (fill in the blank)... then they/he/she would have been more loving towards me. When the truth is that absolutely nothing they did, or could have done differently, would have changed the other person's behavior towards them.
I had a big reality check which confirmed this back in 1997, when my ex-boyfriend who I hadn't seen for 15 years showed up in town and wanted to get together with me. He was a very self-centered person, often sullen, negative, critical, very unempathetic, an officially diagnosed narcissist, who had cheated on me repeatedly with women I knew and had even crawled off to cheat on me the day after I was struck by lightning, in 1979. And now here he was, pretending like we were old friends and everything was just fine between us. When I let him know that this was absolutely not the case, and told him I had no interest in ANY further contact, he began to hem and how how "unforgiving" I was. This made me laugh, and I hung up on him. A day later, he called me back with a very different tone of voice. He said he wanted to apologize for how he had treated me during our relationship. He admitted that he had been "such an asshole" (his words) towards me, that he was ashamed of himself for it. He told me that he had never been able to have a decent relationship with anyone, because of his "issues," and his narcissism, which even many years of therapy had not helped him with. He accepted responsibility for the problems he caused in our relationship, and he told me that he was surprised that I put up with him as long as I did--which was 4 very long years! And then he said these words: "The way I behaved was all about me and my shit. You did not deserve any of it." These are the most powerful words I ever heard from someone who had behaved abusively towards me, and they ring loudly of the truth for all of those who have been in abusive relationships.
This encounter was definitely a gift... a rare gift, from the most unlikely place I could have ever imagined! I had already let go of most of the resentment I had felt for this guy even before he had showed up in town. But I hadn't completely let go of blaming myself for some of his past behavior towards me. After this, it began to sink in that most, if not all, of other people's actions are a reflection of who THEY are, and have little to do with me. This has helped me with accepting reality, and that acceptance makes life much easier to bear.
In general I opt for acceptance over forgiveness. I focus on accepting that the "hurter" is not capable of love, or loyalty, or kindness, or self-reflection, because they have not gotten to that place of inner development yet, and then I let go of the hope that they ever will.