For example, say an individual has grown accustomed to thinking “I am a failure” in response to situations in which he or she falls short of a desired outcome. This thought would then self-perpetuate, thereby resulting in ongoing failures in many aspects of life. This is because simply believing oneself to be a failure removes the expectation or even the remote possibility that perhaps, with enough concentrated effort, that same individual who perceives him or herself as failing incessantly may actually be capable of achieving success.
Positive affirmations seek to reverse this downward spiral tendency, so that a person’s thoughts propel him or her upward into a more positive, contented state. In order to do this, positive affirmations must challenge the automatic thoughts that arise when confronted with various situations in life. If someone is harboring the “I am a failure” belief, then a positive affirmation used to challenge this might be “I am a strong person capable of achieving great success.”
In order for positive affirmations to be effective, however, repetition is key. Ideally, the affirmations will be read and/or spoken aloud several times throughout a given day, or intensively at a certain point in the day, until they become automatic thoughts. The ultimate goal is for these positive automatic thoughts to beat out the preexisting negative ones. Eventually, the positive thoughts will transform the individual’s cognitive sphere into a safe and pleasant source of strength and support. (GoodTherapy.org)