Why "Good" Friday?

So when I woke up this morning - I wondered - why do we call it Good Friday? Why not Tragic Friday? or Bad Friday?  Now remember - I'm a realist - so things from my vantage point are not often gray! In my head,  I do know that sometimes there has to be bad so there can be good - and I know in my heart that I am forever grateful that Jesus died for me - for my sins and the sins of all - but I still have a hard time thinking of it as Good Friday. As much as I'm grateful for this day, I'm embarrassed that we humans have such heart issues and can do such things to hurt others. I remember when we went to the movie version of this time a few years ago and feeling such sadness.....and last night at the living last supper listening to the disciples wondering who would betray Him.....dark Friday......sad Friday.....but Good?