oncepts of mind, self, soul, Spirit, and happiness are closely related in the Holy Quran. They are interconnected, in the sense that understanding them individually cannot be complete without understanding how they are related to each other.
As human beings, we are elated over a lot of God’s creations because of our ability to collect, process, and use data in a good way, by choice.
The human body is just an instrument that incubates and sustains the brain, which houses the human mind, from which the self develops and evolves throughout a person's lifetime on Earth.
God Almighty started the process when He installed an essential software from His spirit into the human DNA, including the brain. This is what allows and enables the human self to start a life-long process of data collection, processing, and decision making while having the ability to differentiate between good and evil.
When the body dies, when it is no longer capable of sustaining the self, whether by old age, sickness, or accidental injury, then records of the human self are completed (ended) by angels.
In the Hereafter, the self is going to be judged on the basis of its performance on Earth. If it is obedient to God in its behavior, it will be living in happiness in this life and in the hereafter. But, if the human self is disobedient to God, it suffers in this life and in the hereafter.
To sum up, goodness is obedience to God and evil is disobedience to Him.
It follows that whatever happens to human beings in their life is going to be good for them in the hereafter, as long as they are obedient to God, even if they become poor, get sick, or killed unjustly. It is good because their ultimate destination is an eternal happy life in Paradise. They have to work as hard as they can in their pursuit of happiness during their first life on Earth but they have to observe God in everything they say or do.
You may get the results you want to achieve here in this life (wealth, power, prestige, reproductive activities, offspring, etc.) but there's a possibility that you may not get what you are pursuing because of circumstances beyond your control.
Success or failure, in the Islamic sense, is in how you conduct yourself during the process.
