This is undoubtedly the worst phase of the "recovery" process. And we've all been there. Sometimes it's so bad that you feel like you have hit rock bottom. But I remember what a friend once told me, "Remember the silver lining... everything from now is only going to go uphill."
We all have our own ways of mourning. For me, it is to literally do what my heart desires at that moment. I like being alone and shutting myself off from the rest of the world... sitting in my room and bawling my eyes out while watching sappy romantic classics.
I've even tried burning my ex's pictures which trust me, made me feel a whole lot better. These though temporary solutions, still work. I wish I could think of something more long-term though. Any thoughts?