There are so many sides to this story, I don't believe there can ever be just one answer. I have also personally experienced situations where I forgave someone for doing something I never thought I would forgive (like being unfaithful).
Perhaps some people can really forget, I don't. I decide if I am going to forgive (based upon the offenders actions after the offense), and then if I do, I NEVER BRING IT UP. That's very different from forgetting. I doubt I could really forget, not if it was something that really caused me pain. But, if I tell someone I forgive them, they can rest assured I will never bring it up, or treat them any differently than before.
As for little things, I let them go very easily. I have been through too many real problems in my life to worry about little ticky tack crap. You have to A) be someone close to me and B) do something really bad to need my forgiveness. Otherwise, I overlook the normal quirks of being human, just as I hope my friends do for me.
I do think, however, that forgiveness depends on the person asking for it. I don't see how I can forgive if I am never asked to.
Happyout