Do you hold grudges against people?

It seems like no matter how bad a person hurt me or caused me trouble, I always forgive - if they put the effort to be nice afterwards. I feel like what they did occured in the past..no point in dwelling on that. I'm always willing to fresh-start the friendship/amity over. Like, there would be times that I wanted to just (*#@&$ kill someone who was causing me such agitation and misery, but just a few days later when the person would be nice to me, I would forgive them without "working" for it. This is only for friendships; relationships, however, are a completely different story.