To forget a bad memory, you need to speak about it with your close friend or relative. You can also opt to write it down and this helps to let it out. You need to occupy your mind with something else to avoid thinking about it.
Turn it into a positive. . .What did you learn from this negative memory? How can you apply it to your future in a positive manner? Acceptance is valuable. My bad and good memories have added to me as a person and made me who I am today. Trust the process.