Damian, for your first answer given, that, "you will never let go" it's not true. You'll never forget it, but it's definite that you will let go. You won't be in love with her forever. If there is no way that you are ever going to get back with her, you better let her go. You need to start wearing a true smile on your face.
Its actually not difficult. Just try to analyze what happened in that relationship. If you come up with REGRETS, you will find it difficult to forget. But if its the GUILT, it would be easier to forget. You just can't forget because you might be the one who gave 100% from your side to maintain the relationship but the other person didnt deserve this.