Positive affirmations help open the door and allow our subconscious to make positive changes in our thought processes and actions. Brain scans have proved that positive affirmations are beneficial.
When you say an affirmation and repeat it, you basically signal your brain, specifically the Reticular Activating System, that what you are saying is important. Your brain then registers the intent of the affirmation as something that is important to you and reacts to it.
If your affirmations are positive, your brain registers it as a positive thought and releases dopamine, which is a feel-good hormone. When you feel good, you act on your affirmations and are successful. However, if your affirmations are negative, your brain registers it as a negative thought and releases the stress hormone, which leads to unhappiness and stress. So, to get positive results, you need positive affirmations. It is like sowing a seed. If you want an orange, you plant an orange seed and not an apple seed.