While motivational messages and monetary incentives are all useful intervention strategies to promote people's physical activity, it remains unclear how these strategies work together to increase people’s steps/day and whether the effect will continue after the intervention period. Here, we investigate how these two interventions affect how adult office workers with sedentary jobs set their goals and achieve these daily step goals. We found that motivational messages can improve people’s walking behavior only when their behavior is first influenced by motivational messages, not through money. Although monetary incentives increase people's commitment to goals, it makes those who with low self-efficacy tend to set easier goals. Monetary incentives may have adversely affect the walking behavior of people who have low self-efficacy. These findings help to shed some lights on how to design persuasive mechanisms for mobile health and fitness applications.