untiring, unremitting, or indefatigable

to persevere unremittingly; to keep going until the end

undisciplined, complacent, or loose in organization or spirit.

impossible to fault; flawless and without any weak points in an argument, defense, or performance

to be idle, sluggish, or lacking in effort and drive

lazy and negligent in one's duties or tasks

to work tirelessly from morning to night (idiom)

slack or lax (of discipline, attention, or effort)

to slacken off or reduce the intensity of one's efforts and resolve

showing persistent effort and not becoming lazy or slacking off