As you probably realize, you are not trying to forget someone, but an obsession that has grown inside you and which does not correspond to any real person anymore. It has simply become an escapist strategy that your mind uses as a shield to avoid moving on.
The best solution to your problem is to find someone real to love. And for that you need to see and feel that the world outside is much more full of wonder and emotion than your interior agonies. Basically do stuff, meet people, be curious about what's around you, go see what's beyond the places you know already.
And have fun doing it!