Compliance with the public health authority guidelines is crucial to prevent the spread of COVID-19 successfully. By analyzing individual responses to a survey, we identify the weakest links, i.e., those who do not follow the guidelines as much as others do, and why they are failing. We find that individuals older than 60 are most enthusiastic in protecting their and others’ health and that those younger than 30 are least enthusiastic. We categorize the factors possibly influencing the precautionary behavior into three groups: preference, belief, and constraint. It turns out that although beliefs on the effectiveness of protective measures do predict individual differences in their endeavors, they do not vary significantly across gender and age groups. On the other hand, risk, time, and social preferences explain individual differences well and significantly differ across gender and age groups. We also derive an implication for managing long-term risks due to fatigue and depression.