DG, What you are experiencing is very normal. You have not failed your marriage, nor have you failed yourself. He is the one that walked out rather than try to work on the marriage. He is the one that took the easy way out rather than do the work that is required to make himself whole and to work with you to make your marriage whole once again. You did not select this path...you were forced to make this journey and this journey will be a lesson in faith as well as one of learning.
DG, in time, things will right themselves enough that you will get your footing once again. Some day, you will wake up and see the sun and smile once more. It won't be tomorrow or the next tday, but I promise you, it will happen.
All I ask is that you be kind to yourself, pamper yourself a bit today and remember that you have many, many friends here who are here to help you along the way....you are a surviver, not a failure.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.