Every minute of every day, your body is physically changing in response to the thoughts that run through your head. Just thinking about something causes your brain to send signals and release neurotransmitters.  What you think, visualize, and say to yourself can change your body, brain and life. One way to harness this power to help you is through affirmations. Studies suggest that positive affirmations can help us respond in a less defensive and resistant way when presented with life challenges. They are a mental health tool that can help you develop a healthy sense of self.
Affirmations are thoughts you intentionally come up with to support, encourage and calm your brain and body. They can be positive statements used to challenge negative, depressing or anxiety-producing thoughts and beliefs. They can also just be general supportive thoughts providing encouragement. Affirmations can be used to influence your thinking patterns, behavioural habits, health and moods. Positive self-affirmation practices can be beneficial in many ways:

Self-affirmations can decrease health-deteriorating stress.
People have successfully increased their physical activity levels using self-affirmations.
Help people perceive “threatening” messages with less resistance. 
Apply self-affirmation as a tool for coping with everyday challenges.
Practicing self-affirmation has been shown to reduce ruminations as well as improve self-esteem, depression and other mental health conditions.
Evidence suggests that affirmations can help you perform better at work. Spending just a few minutes thinking about your best qualities before a high-pressure meeting can calm your nerves, increase your confidence and improve your chances of a successful outcome.