Sometimes I feel that if you truly care about someone deeply enough to try to make a long term relationship work, your feelings never go away for that person. When you spend so much time and energy on something, that energy still exists within us, and it is difficult to put it toward something else when the relationship fails or both parties decide it is best to move on from each other. Moving on is extremely difficult in some cases and one must first grieve it as a loss, and then you may be able to move on to better days. Take as much time as you need to grieve the loss, but do not dwell on the past, try to remember why the relationship didn't work and put some extra energy into the things that make you happy such as a hobby. Eventually you will be able to move on and find happiness with someone else (if that is what you desire). Distance between you and them is a must when you feel the need to move on. If you can not grow separately, you can not grow together, and if you can not grow together, you must try to grow separately.
I don't know if that answers your question, but that is the best answer I can give. This situation is never easy, but with time it will get better.