Right!! I will agree that time is a great healer. As time goes by, you will be able to overcome the hurt and begin a new life with somebody else worth of your trust. I would believe that it is not an easy process to heal the hurt mcht more if you always see the person who caused the hurt. It is better to go away, go to the place where the memories of the past will be out of sight for it would help in the healing process.
I would say, it is not easy to be friends with your- ex if you still have the feeling for her/him. The pain is hard to get rid of if you still have the feeling toward that somebody who hurts you. I know, there is hate and you want to get even then you would also try your best to hurt that person in a way you were hurt. You want to see him/her suffer like you did. That I think is a normal feeling of a human being. It takes time to forgive when you are hurt and much more harder to make firends with someone who hurts you. This is why I would say, it is not easy to make friends with your ex.
When you will be able to accept what you have been through and set aside your feelings toward that person, you are now ready to make friends. Just friends, no hurt feelings, no grudges and feeling of remorse. When you learn to think positively that there is a better future for you and it is not the end of the world when you separate ways, then you will be able to held your head up high and make friends with your ex. I know this is not easy because the memories keep on coming back but in order to be able to move on, learn to forget the past. Charge all of those past to experience. Life is more happier and exciting when we learn to forgive the one who once hurt us and make friends with them.