I feel your pain and also have obsessed over men for years even though the relationship had failed. What helped me was discovering the difference between love and lust.
Love occurs when the recipient gives back.
Lust is that feeling of I WANT that doesn't go away. We cannot control our feelings but we can control our actions. Put that woman in a junk pile, and start lusting after another. If and when the next one turns sour, throw her on top of the pile as well. It does work to keep your mind off obsessing, and the junk pile will grow high, but you will NOT be miserable for the rest of your life.