past, present, future

Yesterday was the past, today is the present and tomorrow is the future.

We should forget the past, cherish the present and look forward to the future, correct? Hmm..then why can't i forget the past? i very much want to forget it, get over it, pick up the broken pieces and move on but i just cant do it.
What am i going to do? Though i tried my very best to forget it, it will pop up again suddenly, catching me completely off guard, affecting me in all kinds of ways. Sigh...i need a memory loss potion..haas.