Depends on which emotion. Id look at the tea and its qualities and chemical composition to interpret if it works for the mood you are hoping to attain. Depressed and need to fight it? Black tea. Want to be happy and creative? Yerba Mate. Want to be evenly balanced and learn new ways of looking at stress? Rooibos. Want to be totally focused and cool and collected? Green tea. Qualities of tea can be categorized as yin and yang. Given mood states, outdoor temperatures, state of season(winter eg.), environmental stressors can influence which tea works for you. I work in a hospital so I always include a bit of black tea in the mix as it is combative and staff are moody so I need to fight that in addition to fighting possible illness from all the bacteria running rampant.