Affirming yourself can be done in many ways, using positive affirmation whether in writing, speaking, or listening to them from a recording allows you an opportunity to replace those negative thoughts. The psychology theory underpinning how affirmations work is called self-affirmation theory.

Minakshi, R. (2020). Positive Affirmations and its Benefits on Psychological Well-Being. Journal of Psychological Science. Vol 13, No 1. 

Cascio, C. N., O’Donnell, M. B., Tinney, F. J., Lieberman, M. D., Taylor, S. E., Strecher, V. J., & Falk, E. B. (2016). Self-affirmation activates brain systems associated with self-related processing and reward and is reinforced by future orientation. Social Cognitive and Affective Neuroscience, 11(4), 621-629.

Sherman, D. K., & Cohen, G. L. (2006). The psychology of self‐defense: Self‐affirmation theory. Advances in experimental social psychology, 38, 183-242.

Cohen, G. L., & Sherman, D. K. (2014). The psychology of change: Self-affirmation and social psychological intervention. Annual Review of Psychology, 65, 333-371.