Q. What constitutes the zenith of happiness and the abyss of sorrow to a human being?
                                                                  

Understanding that he is the limitless source of happiness is the zenith of happiness to a human being. There is nothing beyond that. 

The worst tragedy to befall him is forgetting the Lord who has blessed him with such a blissful life. Our ancestors opined that two types of persons must be sunk: 

Those who do not perform charity and those who do not seek God even when they have fallen to sorrowful times. Your prayers grant you material wealth. And you have to do charity to gain a good after-life. This is the route to attain salvation.