How do i let go of the past?

Ok so we have been married for 4 years been together for 16. We have a very rough past. He is currently deployed to Iraq and did sum foolish things that were the last straw for me. This happened in april of this year. Just recently we have started talking again, and seeing eachother on webcam. We both know that we do not want to go back to the way things were because we were oth unhappy. So my question is how do u let go of the past? How do u not let it effect the way u think and trust? Theres been soooo much that has happened in the past i cannot help but to think of things and automatically ume they will happen again because they do. How do i know that it wont happen again? I had faith and hope for so long but it ran out. But since we have started talking again, ive realized that i do love him more that anything in this world and i want to do what it takes to try and to see where this is going to go. And in doing my part, i have to learn how to let the past go. Please any suggestions are welcome!!!