Buck Fever

[FFKEVIN]

Alright, I'll admit it.  I had buck fever bad...
 
This past weekend I had a BIG buck catch me off guard and come in behind me.  He almost busted me.  He looked at me for a while and I just sat as still as I could.  I guess he decided I was nothing, because he finally turned broadside, 25 yards away, with his head behind a tree.  Perfect shot right?  Yea except, my heart was beating so hard I thought it I was going to have a heart attack or that my heart would just beat right out of my chest.  I could feel it beating in my ears.  Needless to say I rushed the shot, missed and hit the tree.  I've been thinking about it since.
 
Anyone have any advice or tips on how to beat buck fever???