This is what helped me. Find something good that you contributed to the relationship and affirm that they will come back because they know they won't find someone that did so and so better than you. For example, say you were a good woman and you know no other woman will treat him as good as you treated him, that's a great affirmation because it's not a lie, it's true and they probably won't find anyone else like that. This may sound small, but it definitely helps with trusting and letting go.