Make sure that all relations with this girl is over and she is absolutely not interested in you. It is unlikely you will be happy if you can forget about it and later found out that all this time she was hoping you would approach her and resume the relationship. Do not give up your happiness ahead of time. Only if you know that you two have no future together, start to take some action.
Don't try to suddenly let go of all thoughts about the girl you love. Such drastic measures may help at first but a few hours later, all thoughts and feelings flooding back with renewed vigor. Rid yourself of feelings of love is very difficult, but that's what you need to do, because feelings make you constantly think about it.
Take all my free time. Minutes of idleness will be required to return you to your object of love. At work, ask the head of the additional load it will be only glad for this initiative. In the evening go to the fitness club or find yourself another hobby, good for the soul and body.
Try to pay attention to other members of the fairer sex. Thoughts about the new girl will make you forget about the failed relationship. There are so many worthy and looking for the love of women, you only need to open for them. The best cure for unhappy relationships - new love. Perhaps the new girl can bring to your life what you missed.
Behave decently. It is not necessary to grovel before the man who to you is absolutely indifferent. Convince yourself that nothing happened, so the fate has saved you from a bad marriage and more pain. Don't lose confidence. You'll be lucky, and there will be the kind of girl that will make you happy.