The skill part of self hypnosis requires time to develop, and some people take longer than others to get good at it. We don't know why. It is not related to intelligence (within normal bounds) or any other variable that has been reliably and consistently identified. Some people see results immediately, while others may take several days or even weeks to notice a difference. With proper application and daily practice, though, you should begin to see definite results within 21 days at the outside.