I feel monotony and death to be almost the same.

The line equates a life drained of change, purpose, or stimulation with a kind of living death. Brontë often portrays intense inner life chafing against constricted circumstances; in that light, “monotony” is not mere boredom but a sustained condition of enforced sameness that erodes vitality. The statement suggests that what makes existence feel fully alive is movement—emotional, intellectual, or experiential—and that when this is denied, the self experiences a collapse of meaning akin to death. It also implies a moral urgency: to accept monotony passively is to consent to a slow extinction of the spirit.