Life.
Letting go, even if it hurts, doesn't mean you have to let go of everything. You just have to let go of the person and your feelings for her/him but the memories will always be there whether it's good or bad. Because everytime you remember those memories, it will always put a smile into your heart. And be glad that once in your life this person made you happy and put colors into your life even if it's just for a while.
Lot's of love.