This study aims to develop mathematics lessons for high school students that encourage the use of mathematical activities that enable the students to develop the ability to think continuously during mathematical tasks. Special lessons were conducted and questionnaires were given to the students. The findings suggest that there are four key points to be noted: 1) applying mathematics to real-life situations is important; 2) tasks should enable students to experience the pleasure of thinking; 3) ideas can be improved through communicating with others; and 4) a sense of accomplishment should be achieved. Therefore, it is implied that focusing on these points enables students to become motivated and to have positive attitudes toward mathematical tasks, which leads to the development of the ability to think continuously during mathematical tasks.