RE: why do we get buck fever?
I have a one word explanation as to what causes "buck fever"!!!
ADRENALINE!
The wonderful stuff that seems to give people super human strength, or an ability to walk on broken legs.
Adrenaline is released from our adrenal glands (on the tops of our kidneys) into our blood stream in exciting, or stressful situations. Adrenaline causes many physical effects. Such as increased heart rate, increased respiratory rate, dialation (opening) of blood vessels, constriction (tightening0 of muscle tissues, an increase of glucose into blood stream, and an increase of glycogen being converted into glucose. It is a hormone that chemically tells our body to go into 'high gear' (like nitrous oxide in a racing engine). It also has an effect of inhibiting pain receptors, and giving a mental effect of 'everything going in slow motion'.
Once adrenaline is released you will become shaky, and have trouble controling your heart and breathing rate. Muscles will tense, and respond to the slightest input telling them to move. This is where many misses in hunting occur as your body over responds/corrects to recenter you aim. It also can cause your 'squeeze' of the trigger to be more jerky and 'pull'-like.
This effect can be controlled, but only experiencing an adrenaline rush and working with it rather than fighting it will be able to help.
Some advice I can give, for what I do, to work with, and harness the adrenaline 'rush' is to focus not on the deers antlers or overal prescence. But to focus on a certain point on the animal (such as the exact point you want the projectile to impact on the animal. This focus will help you calm the effects of the adrenaline and slow the release of more of it into your system.
Hope this gives a little understanding to how and why we get 'buck fever".