If happiness always depends on something expected in the future, we are chasing a will-o'-the-wisp that ever eludes our grasp, until the future, and ourselves, vanish into the abyss of death.
We begin from the recognition that all beings cherish happiness and do not want suffering. It then becomes both morally wrong and pragmatically unwise to pursue only one's own happiness oblivious to the feelings and aspirations of all others who surround us as members of the same human family. The wiser course is to think of others when pursuing our own happiness.
If Allah has written for you happiness, no one can steal that from you, and if He has written for your heart to break, then no-one can mend it but He, so always put your trust in Allah.
The activity of God, which is transcendent in blessedness, is the activity of contemplation; and therefore among human activities that which is most akin to the divine activity of contemplation will be the greatest source of happiness.
Happiness of any given life is to be measured, not by its joys and pleasures, but by the extent to which it has been free from suffering-from positive evil.