If something great happens that makes the player exalt, the in-game character should do the same as well. For instance, if the player gets an awesome power-up that gives him exciting new abilities, the in-game character should be excited by that as well.
However, if the character has a large exuberant response to every little reward you get in the game, but the player doesn't feel the same way about receiving those rewards, the player will start to break his or her emotional connection with that central character.
The opposite also holds true. If you feel excited about a big accomplishment but your in-game character has no reaction, that can also diminish or break the bond.
The exception is if part of your character's Diamond is to show no reaction to triumphs or setbacks.