Personality is the collection of characteristic thoughts, attitudes, feelings, and behaviors that impact how we view ourselves and what we believe about others and the world around us. In general, personality trait s are relatively stable characteristics, but states are transient. Research has shown that our beliefs and attitudes are learned and shaped by our own experience and expectation, and that these are not fixed and can be changed. Studies have shown that mindfulness induces state changes that influence cognition, feelings, and corresponding brain activity and connectivity after short-term training, and traits changes are also found following long-term practice. This chapter explores how traits and states contribute to mindfulness practice, and explain how this knowledge could improve our practice efficiency.