Affirmations are positive statements you can use to reframe how you think about yourself and the day to come. They are a way of visualizing the good things that will come to you that day and overcoming negative self-talk.
In his book The Miracle Morning: The Not-So–Obvious Secret Guaranteed to Transform Your Life (Before 8AM), Hal Elrod says:
When you actively design and write out your affirmations to be in alignment with what you want to accomplish and who you need to be to accomplish it—and commit to repeating them daily (ideally out loud)—they immediately make an impression on your subconscious mind. Your affirmations go to work to transform the way you think and feel so you can overcome your limiting beliefs and behaviors and replace them with those you need to succeed.