I don't "get" this philosophy, re prison, that says that (paraphrasing,) "If your head's right, you only do two days; the day you go in, and the day you come out."
Somehow I don't see these guys going to happy places in their minds.
You're right; most prisoners don't see prison that way. They view prison as an inconvenience and don't learn their lesson (actually feel guilty, acknowledge they deserve to be there / repent), and most come out with more criminal skills and mindset rather than law-abiding citizen or new job skills.
But, in the rare case someone does have the right, morally speaking, mindset, they stay dedicated to shaping up before shipping out. And, likewise, this can be described to represent someone going in and out who's a scumbag recidivist street thug who does the time as this sort of 'trial' and right of passage that gangs and criminals view prison as part of their lifestyle choices- a natural part of the game.
----- 1 out of every 1 person will die; our mortal frailty is humbling. Pursue your ultimate good.
I take it that you'd agree that the characters in this show sentenced to prison fall into the latter category - except, perhaps, D'Angelo? Do you think they view the "days in between" as an opportunity (if a forced one!) to hone their skills, so to speak?
I think what they are saying is that those two days are the hardest because on the day you go in, you are losing your freedom and that is the most jarring for people. On the day you go out, you are anticipating getting your freedom back, and knowing what that will be like, combined with the fact that you still are being confined, makes it hard.
If you work a 9 to 5 job, Monday through Friday, you can relate on some level to this philosophy. Everyone hates Mondays because it is the first day back after two days of freedom. Fridays seem to drag on forever because you're anticipating getting your freedom back. The other three days are mundane in comparison.
I think the saying is there to help people wrap their head around sentence length. You are doing 2 years, but really the only 2 that matter are the 1st and last. Anything in between you shouldn't mentally focus on.