Is it better to be very excited or more level with your emotions on the golf course?

Great question!

First of all, it is important to be yourself, to have authentic reactions, and then learn to respond in ways that are constructive.  We all have emotions, and emotions are part of the passion you have for performance.  So, it is ok to have some emotional reaction.  The problem lies in when you feel a round is a complete emotional roller coaster, and the highs are too high and the lows are too low.   These kind of emotional reaction will likely impede performance.   Learning to channel emotional energy constructively so that your emotions support performance is the ability you want to develop.

Here is a more detailed response on developing good emotional management for performance in sport ~

  http://www.aheadinthegame.ca/2011/09/why-emotional-management-is-a-key-mental-performance-skill/