A strong belief in free-will correlates with an internal locus of control, which enables a "growth mindset", an external locus of control does not enable a growth mindset because the human believes they react to things.
I do have to admit that for a good while, accepting absence was not good for both my mental well-being, or my actions, simply because I could not find meaning or reason to do anything when no choice is ever my own.
Absence of free will however, implies that there is no locus of control at all. Things happen as they will, regardless of what any human believes, and accepting that things just happen and going with the flow is something that many eastern religions advocate for.
The consequence of accepting the absence of free will is that the person can stop dwelling about the past, because they were never in control and could have never done otherwise. The person understands that any action they "take" is conditioned on their brain's current state (ie structural and chemical).
This means that nothing is fixed, the person itself is not fixed in place because the person is a manifestation of the brain's state, which is constantly modified and revised.
This assumption then, even if wrong, enables a much stronger growth mindset, one that doesn't dwell on the past, and doesn't get stuck on misfortunes, or on a false sense of optimism.
By accepting that we lack free will, we "can" then probe our world model to see what makes us happy, ie what utility functions our brain has, which then gives us a compulsion to do things that make us happy or reach goals. This is because we understand that what needs to be done is change our brain's structure such that when the time comes, it will be in the correct state to achieve whatever it wants to achieve, and understands that achieving goals and pushing forward makes the brain happy - even if only momentarily - due to dopamine.
On a larger scale, suddenly inmates are not the evils society makes them to be, but people who have a screwed up brain and that need help, rehabilitation and normalization of their brain and structures so that they too can experience a decent life, and the events that got them imprisoned can not unfold again. Obviously this does not mean that the inmates get thrown back in with the general population (pun not intended), and that is because they are still in a space of states that cause them to be dangerous to other humans.