How forgiving are you?

To be completely honest I have never been put in this situation, except in my past when a boyfriend of almost 1 year cheated on me, and it broke my heart. Only it was alot easier because we weren't married. As soon as I found out, it was over. I broke up with him right away. I am worth more than that. Some people are forgiving on these types of things, my best friend being one of them, her husband has cheated on her a million times, including with her own sister (yeah..I know). But I personally couldn't forgive something like this. I have thought long and hard about this before and I honestly do not think that I would be able to stay. One of the main reasons being that I know in my heart of hearts that I personally would never be able to trust him again, ever. Once someone breaks my trust, it is pretty much broken. That's it. I know we are supposed to forgive, but I'm sorry, that just isn't in me when it comes to something like this.