For me working my program helped and practice ,practice,practice..shutting off those thoughts when they happen, recognizing the obsession and letting the thought go is lke working out..the muscle gets stronger.When I first started i had no control over my thoughts..alanon literature and buddihst readings as well taught me I can have more control and not be so at the mercy of my monkey mind. Jamaicame's suggestion is right on in my opinion..staying in the present, the now instead of future tripping or dwelling in the past is very healing.It does get better and I don't think you ever totally get rid of that sadness, but you can be happy and free of obsession..