lack of confidence in their ability to be physically active (low self-efficacy) fear of being injured or having been injured recently. lack of self-management skills, such as the ability to set personal goals, monitor. progress, or reward progress toward such goals. Lack of confidence can be a barrier to physical activity. People who are shy or lack self-confidence may be less likely to participate in physical activity, even if they are physically fit. They may be afraid of making mistakes or feeling embarrassed. In addition, people who are shy or lack self-confidence may be less likely to stick with a physical activity program.