Instead of giving yourself the messages that provide excuses (I'm not an athlete, I'm not the kind of person who loves tofu, I'm not...) give yourself permission to become the person you think you aren't. You are not truly limited by who you are, but by who you think you are not.
I am an athlete. I am successful, consistent, and motivated. I am the kind of person who falls down (a lot), and gets back up every single time.
Then ask yourself - does what I'm doing match who I am?