Loneliness

 Although there's always Hope in prison, everyone is lonely.  Separation from family and friends makes inmates desperately lonely.  Also, since the inmates aren't sure of whom the other inmates are, they also distrust everyone and everything.  That's isolating individuals from each other.  The only remedy is visitations from family and friends and writing letters and phone calls (this costs money).  In fact, postal stamps are used as money when inmates trade with each other.