When a prisoner is about ready to be executed they're usually given a sedative to prevent them from fighting during the walk to the execution room.
Also prisoners who are about to be executed are given their execution date prior to the execution and are given time to prepare for the execution.
Sometimes a pastor within the prison will speak to the death row inmate and get them prepared for death and some prisoners are just ready to get it over with and not be on the death row anymore.
Being on death row could make you want to die soon because there's nothing for the prisoner to really do and it has got to be more boring on death row in an isolated cell unlike in regular prison population.
The prisoners on death row also know that if they fight the walk to the execution room then they'll not win anyway and still be taken and put to death.