That depends on the brand of mysticism you prefer. Early forms of Buddhism would agree- that which was reborn was the accrued karma. Living a life of enlightenment let you die without karma, ending the cycle.

On the other extreme end, Christianity favors a version where the soul is responsible, and held in judgement. Some branches allow for purgation, others are a "go straight to heaven or hell" variety. What's the point of rewarding or punishing a soul that had no agency in life? What of a soul that was shaped by a brain fundamentally different at death than early adulthood?

Orthodox Christianity is a little different- there's purgation, without the purgatory. Moreover, the goal in life is theosis- living in such a way that your being aligns with the holy Spirit, essentially attaining sainthood while alive and in direct communion with the divine.

So, many very opposing answers, the truth of which is beyond me to decide for you.

>What's the point of rewarding or punishing a soul that had no agency in life?

So we're to assume that the sensibleness of doctrine is what determines the underpinnings of reality, that some kind of Just World force makes the world work in a way to minimize the injustice resulting from it? That makes even less sense. And anyways, the evidence suggests that such a force is not dominating the other fundamental forces.