How can one let go of unwanted memories?

In life, there are some memories we want to keep it forever, however there are some which is not that happy that we would want to forget. The question is how can one forget or I should put it "How Can One Let Go of the Memory He/She Doesn't Want?"
Does it involve mask? Hiding your true self when it come to facing that problem?orAllowing yourself to continue getting hurt for the time being till one day (don't know when it'll come)?orJust say what you feel without caring about the other party's feeling (burden/stress)?
The main question of mine is also related to "Do you prefer to hurt yourself or to hurt someone you love?" How can this be answered?Stingy people who cares for themselves will answer they are the most important thing. However, for those who is caring (I doubt so whomever out there is like that) will choose to sacrifies themself.
Relates back to my previous post, "Life", we are full of choices to make everyday. If you were to let go, you have this kind of ending. However, what if you choose the other one? No one will ever know the answer because each one of us has different life and we live our life differently from another person. So the experiences that we are going through daily is different. So the other road that is not chosen is something where one can fantasize however they like and regret on this very road that they have choosen and is walking on currently..
Another point where one can lose an unwanted memory purposely and it can be accidently is through serious accident that involves brain. Lost of memory would be the best because those memories will not haunt you and you can totally start a brand new life.. The 3 suggestions that I have mentioned will never work for the rest of your life, as long as you live.. Memories can never be erase.. Time cannot be turned back.. Mistakes cannot be undone.. Water that has been poured away can never be collected back..