Do you feel like you want to beat this fast rower? Do you feel extra energy on training when you think about the pleasure of winning that race and being the fastest? Do you find yourself setting goals on getting higher on the ranking? Do you look to the future trying to get better results and more speed?
If your competition keeps you focused and motivated consider yourself lucky. Having rivals is one of the better motivations to stay heads-down on producing the highest quality results. Your competition provides balance to an equation. If you are unbalanced on this equation you can possibly become complacent and relax too much and get slower.
The moment of victory is often the moment of greatest peril. In the heat of victory, arrogance and overconfidence can push you past the goal you had aimed for, and by going too far, you make more enemies than you defeat. Do not allow success to go to your head.