Like all Zen statements this one sounds a lot easier then  it seems.  Letting go sounds easy but requires considerable training over a long period of time to achieve mastery.  Let go of hurtful comments made by bullies, let go of anger, let go of things that hurt you.  This is not always but you always have a choice.

Are you happy now?  If not why not?  Only you can make yourself happy.  What are you waiting for?  Don’t delay your happiness till sometime in the future.  Choose to be happy now.