There is a popular sentence in our language which says:
Literal translation: Always, take your competitor/rival seriously.
Connotation: if you are going to defeat your rival during a match, you cannot thing as if your rival is weaker than you. Because if you continue thinking like that, you might lose the match while you've adapted your mind to a specific mindset regarding them and they can shock you during the match. So it would be better to consider them as even more powerful than they are so that you will not get shocked when it comes to the competition (if they are stronger than you.)
This is a term which comes from our ancient wrestling culture and I need to inquire whthere there is any fix quote about it or not.
Also, I wonder if you let me know whether my own self-made translation using both words "competitor" and "rival" works naturally or not.