How the theme developed in a lesson before dying is isolation

Grant and Jefferson are not blood relatives, they are connected through their common experiences as black males but both are isolated. Grant lives in a mental prison of his own making created by his hatred of whites and detachment from those who care about him. Jefferson is physically isolated in prison. This of course means mental isolation as well.

what theme about isolation is developed in a lesson before dying?

what does grant mean when he states "not realizing that their holding on will break me to"