This misstatement comes in other forms, too, such as “I’m not smart enough” or “School was never my thing.” The fact is your brain was designed to learn, loves to learn, and knows how to learn, according to Rita Smilkstein, Ph. D. 
It learns with practice as over time it literally constructs a new neural network specifically for that object of learning. Learning takes repeated exposure to material over time, ideally connecting it something we already know. It also helps to be truly interested in the information and confident about your learning. The truth is “I can learn anything I’m committed to learning.”
Source: Smilkstein, R. (2003). The Natural Human Learning process – Tools for Writing. Retrieved from http://www.toolsforwriting.org/uploads/5/4/3/6/5436311/guidelinesbornto_learn.pdf