When you really, truely, think about what happened on that Friday there is nothing good about it, unless you know the ending.
Judas betrays Jesus for 30 pieces of silver. Which he then regrets and then hangs himself. The disciples are asked to stay awake while Jesus prays and they don't. Peter denies Jesus not once, not twice, but THREE times. Jesus is falsly accused of things he didn't do. A murderer is set free while the only truley innocent Man is sent to the cross. Even before the cross though, as if that is not aweful enough, he was beaten over and over and over again until His back became like hamburger meat. And, if that is not pain enough the Man who had instant access with God was forsaken because of the sins of others, of myself. If this was the end of the story there would be no good.
But it's not. :) And that is why this Friday is good. Because there is more to the story. The Man who was innocently put to death was raised again on the third day. Those sins that He bore...He did it for me, and you. Peter, the same person who denied Jesus three times, was affirmed three times after Jesus' ressurection.
It is so important though, for the full joy of Easter to be experienced, to remember the pain and sorrow and suffering that occured on Good Friday.