csc,
Anger is something we're all familiar with here, you're right. Sometimes the anger and the hurt are so big that they seem insurmountable.
And they may be -- it just depends on a lot of things. But if you want to try, a good thing to start with is, like Best says, NarAnon meetings. These are meetings for loved ones, not the addicts themselves. People share what's happened, ideas, solutions, and just plain support. They can help you get to the root of where precisely your anger lies, and maybe even help you defuse it. For example, I learned that much of my anger (probably 50%) wasn't anger at my X, it was anger at myself for having not been strong enough or smart enough or observant enough or WHATEVER enough to save myself from the pain he dished out.
The other 50% was my soul's way of telling me that I was staying in a relationship that was unhealthy for me. For me, the anger and hurt accumulated over many years along with infidelity, lots and lots of lies, and general irresponsibility on his part. I stopped and looked carefully at the relationship and decided that it wasn't anything like the kind of life I wanted to be living. I wanted someone I could trust, someone who wasn't a ticking bomb for relapses the rest of our lives together, and someone who detested lying as much as I did. The anger was telling me: you don't belong here.
But you have to think on all of this for yourself -- think about what YOU want out of life, and write down the traits that you need & want in a life partner, the ones you admire in others, the ones you dreamed of as a girl. If your fiancee is simply too far from the person that you KNOW you want for yourself, or if you're not willing to live with the risks and challenges of being married to an addict (all the costs, lies, risk of relapse, etc.) then you have to act on that.
In the meantime, take care of you. Keep developing your own strengths, goals, dreams, friendships, LIFE!
He needs to take care of his side of the street, you need to take care of yours.
So sorry that you needed to find a place like this, but so glad you found us anyway. There is a lot of support and kindness here.
Hugs,
GL