Possible Clues:

• In other words, in man it�s a state of mind
• It may need boosting
• Mostly extra beer causes spirit of optimism
• U.S.O. shows boost it
• Degree of confidence the writer includes in speech
• There's more about the spirit of a half-century
• Self-confidence Sir Thomas displayed crossing a lake
• Gypsy coming back with beer and spirits
• General level of confidence or optimism
• It's sometimes boosted