Forgiveness

I have been seeing a therapist lately. I think I've been somewhat depressed for a few years, and I'm not really sure why. My major problem is anger; I get unreasonably angry at people who don't deserve it, mostly my son and husband. She is really great to talk to and so far just having someone who just listens to me has been a huge help. I was talking to her today about the fact that I can't seem to forgive and let go, that I tend to hold onto things when I should forgive as I am forgiven. Why do I mull these things over? Why can't I move on? It's like poison, like Gollum and the ring. She reminded me of the Lord's Prayer; "...forgive us our trespasses, as we forgive those who trespass against us..." Not that God is holding it over us, that if we don't forgive He won't forgive us...or is that exactly what He's saying? If I can't forgive, what does it mean about my salvation? Either way, ouch.