A lesson learned
Joy is a by product of spending yourself in the love/service of others. The happiness found by pursuing the self's interest is like a soda pop: fun tasty, but really empty and leaving you with less than you had before you drank it. Only when your live and happiness is in second place to the live and happiness of others will you truly find satisfaction.
Humans are made to be part of a Community, each serving and loving each other, a solo Human - even in a crowded room - is a failure. How to achieve this? God knows.