How do you forgive when you are still angry?

I don't think this is a skill I ever picked up. Moving around so much in foster care, you didn't need it. You just picked up and left the problem there. I feel like a kid asking this question, yet here I am at 27, not really sure how to do this. It's feels pretty pathetic.

He did wrong. He went behind my back and betrayed my trust. And I know I still wouldn't have known if I hadn't of opened his bank statement. What does that say about him? Does he deserve my forgiveness? I know to a lot of people, money is not that big of a deal, but to me it is. And when he keeps trying to justify it, it just makes me even angrier. I mean, how do you look someone in the eye, and lie to them, without even blinking? I think that's what makes me feel the worst. That he lied to my face, over and over, and I didn't even know. There wasn't even a hint.

How do you trust a person knowing they can lie like that? Especially after allowing yourself to trust them in the first place? I feel stupid. That's how I feel. Stupid. Maybe the problem was letting my guards down. I stopped looking for the lies. I allowed myself to trust him fully. And I was wrong. He could do it. Lie, even over something as trivial as money. And it's why I can't trust his excuses.

And the bad part? He still doesn't get it. He still thinks I am over reacting. And I can't get him to see the real point. And I am tired of trying.