Forgetting someone is not an easy task. If you had spent some quality time with a person for long and really got intimate with someone, it is hard to do away with the thoughts of someone when both of you decide to part ways mutually. Break-ups can be tough and hard to bear and forgetting someone who was once your beloved requires you to initially accept the fact that the other person is no longer with you and does not have any stake in your life.
Forgetting someone is easier if you decide to let go and begin on a new journey of life. Let your life start afresh treating it like a blank slate where you have the power and the will to script your own destiny. Don't be a slave of your past. Everything around you is in motion and nothing stops. So, forget someone if there arises a need.