句子1(主題)saves people/students a great deal of time by eliminating hours spent on hesitation, so they would be able to concentrate more time and energy on their academic/meaningful work.
句子2(主題),occupying spare time so constructively, makes a person contented, with no time for boredom/wondering and helps them achieve a more broaden horizon.
句子3 As we all know, the days of youth should not be frittered/idled away and time should be cherished, but (主題) wastes hours, lavishes days and even squanders years, which leads us to say it kills and even murders youngster’s prime time.
句子1 (主題) makes people weary of other important things, discourages them to learn more, and they finally lose their interest to learn, which leads to their low grades/ low efficiency/ underachievement.
句子2 One’s energy gradually wears off and one’s thought, creative thinking and exploration spirit have been stifled by doing (主題).