'I know' can close an otherwise open mind, can shut down an ability to learn something new, and can stop you (and/or someone else) from getting something amazing. These two words are often used based on our own experiences and can nurture a limiting belief.
So what do you know? Do you know you probably won't get the promotion? Do you know what your partner is going to say or do next? Do you know how competitive that industry is? Do you know you're not the kind of person who could....? Do you know what is good/bad for your business?
Before you say 'I know', just stop for a moment. Open your mind to new possibilities, new learnings and new perspectives....you never know what might happen.