Mahatma Gandhi once said, “Man often becomes what he believes himself to be. If I keep on saying to myself that I cannot do a certain thing, it is possible that I may end by really becoming incapable of doing it. On the contrary, if I have the belief that I can do it, I shall shortly acquire the capacity to do it even if I may not have it at the beginning.”
His insightful comment likely preceded the development of cognitive behavioural psychological theory. Cognitive behavioural theory is based on the notion that changing maladaptive thinking leads to change in effect, attitudes and behaviour. What you think begins to crystallise into your attitudes and those attitudes begin to manifest themselves through your behaviour. I think of attitudes as clusters of repetitive thoughts. If your thinking and attitudes are unrealistic, dysfunctional or otherwise problematic, then your behaviour will likely be the same.