The energy derived from certain emotions can be constructively channeled into specific activities. This is similar to the constructive use of electrical capacitance stored in batteries and capacitors to drive electronic circuits.
Pent up emotional energy can be released by processing it in some way and channelling it into a useful pursuit.
Love is a complex emotion which helps bring people together. This ranges from the lust of a wedded couple to the belongingness of a Church congregation.
When a person is sad their body is telling them to relax and let go of tensions in the mind and body. Sadness is letting go.
Humans are a naturally aggressive species. Emotionally fit people are those who have learned to channel their anger.