Moving forward after the pain of divorce

How do I deal with the brokenness of divorce and make a new life for my kids and myself? I'll admit that I've made some bad choices. One of the worst was walking away from my family when my marriage got too tough to deal with. I realize now that my absence has not only brought me personal pain, but has had a negative impact on the lives of my kids. What's done is done, and there is nothing that will undo the harm I've caused. I feel extremely guilty. Where do I go from here?