The gifts of intelligence and the freedom of will, to accompany the marvelously designed human body, these were the things to which human beings were entitled to, by their very nature. But that was not enough for God. He wanted to give more. He also bestowed on Adam and Eve the preternatural (beyond normal) gifts of freedom from suffering and death, great wisdom, and perfect self-control. But the most precious gift was the supernatural gift of sanctifying grace, the bond of intimate union with God.
These gifts were to be passed on by Adam to his descendants...
But the one thing that was required of Adam in order to secure these gifts was that he must freely out of his own will, give his love irrevocably to God. This was the purpose of man's creation: to give glory to God by their love for him, and in that love find eternal happiness.
But Adam and Eve rejected God. And so the preternatural and supernatural gifts were lost. All that remained were the gifts that man were entitled to by their human nature. The sin committed was not Adam's alone. Because all of us were present, potentially, in our common father Adam, all of us were affected when he sinned. 'Because our human nature fell from grace in its very origin, we say that we are born 'in the state of original sin'.' The stain of original sin is not something 'on' or 'in' the soul. Original sin like sin is a no-thing. And so it is something that is absent from the soul. A state where we are depraved from sanctifying grace...the ability to be in union with God.
People often ask, "Why must I suffer for something that I didn't do? It was Adam's sin, not mine. I wasn't even there!" And then they might further add, "God's not fair!"
The gifts lost to us were not the ones that we were entitled to by reason of our human nature. Those were the 'extras' that would have been ours if Adam had obeyed God. It wouldn't be right to blame God.
If, long before, lets say a man named Bob, was born, some wealthy man had offered Bob's dad a huge huge sum of money for a small job, and Bob's dad turned it down. Bob can't blame the wealthy man because he is poor. It was his father's fault. Not the rich man's.
But even though we lost all the preternatural gifts, God in his infinite mercy did restore to mankind the most important gift-sanctifying grace. Jesus Christ's death on the cross has restored that gift to us which we receive through baptism. And we should all be thankful for that. I know I am.
Ref: The Faith Explained by Leo J. Trese