If it hasn't been lost already, prison strips us of potential and forces a narrowing of one's concerns to basic needs and the will to live. Not that living is physically difficult in purgatory, but a will to survive demands a desire to exist beyond the restrictive nature of the prison. Living outside of this box means leaving behind petty, hateful, selfish concerns and degraded thinking. It means leading by example, sharing empathy and understanding, and striving each day to be a better person. This goes against the central purpose of incarceration.
To create significant choices in a very limited life there has to be comprehension of what it means to have free will. There is no need to live and think like an animal even as the state accuses us of being one. Old ideas of what is or isn't deserved treatment have to be replaced with a sense of personal responsibility: this is my life and I am in control.
The freedom to think in terms of what "could be" is a crucial skill one must develop on a daily basis. Without it, considering the future and recognizing one's potential is impossible. Only our awareness of this power can spare us from squandering it.