help with limiting beliefs

i have been following subliminals for a week no results. thats fine, i know not to just magically grow to 6'5, but like in the mornings ill check the mirror on instinct and say to myself that subliminals dont work. ill also find myself randomly thinking it when listening and then quickly trying to tell myself thats wrong and that i do believe. i truly do believe but i sometimes just get these thoughts and always feel the need to measure myself/look in the mirror for results and i think thats the reason im not seeing it. if anyone else has dealt with this how do you fix this/shift the perspective?