Robin Williams was lost to depression.  He knew what it was to feel overwhelming sadness and despair.  I don’t think he’d want anyone to be sad on his account — he spent most of his life making us laugh, after all.  Honor that.  Go watch one of his movies, or watch clips of him on youtube, or google some of his quotes, or just recall your favorite memory of him.  But whatever you do, make sure to laugh.  I think he’d want us to celebrate his life, not mourn his death.