I'm sorry you're going through this
Try not to be hard on yourself. True, your ex did not deserve everything you gave him, but at least you gave your "all" to the relationship and can look back without regretting that you didn't. You can know you did your absolute best, and that he's the one who didn't. He's the one who will regret losing you, but now you get to spoil yourself: with movies, taking yourself out for lunch, getting yourself a massage or manicure, etc.
It's okay to mourn the loss of your relationship for a little while each day (set aside 15 minutes each day, or however long you need), but it's all about you now, and you no longer have the stress of listening to his complaints! When your "mourning" is done for the day, you can just be good to yourself allllll evening/night/weekend long. That's a very nice thing, no?
One day, you won't miss him. You might think about him every day, but you won't MISS him or have regrets anymore.
Remember: you you you. Splurge on YOU.