The Higher belt: Teaches you, helps you, inspires you, pushes you and makes you realize you need to train more.
The Lower belt: YOU teach the, help them, inspire them,push them and make them realize they need to train more.
No matter how much mat time you have, how well your brain retains techniques, how naturally athletic you are, there is ALWAYS someone who can help you to be better (and that isn't always someone who is better then you-or bigger or stronger)
It's great to have a training partner equal to your size and skill level but, for some of us that isn't always an option.
I train with adult men weighing over 200 lbs to kids weighing under 80 lbs, some who are new, some who have been training many years.
I try to get something from every roll, if its the big guy, I try to work on my defense, speed and trying to move ME instead of trying to move them. If it's the little guy (or girl) I try to work on my technique, maybe try some new things.
Sometimes I have felt as if I'm taking someone else's "quality training time" but, the truth is, they could be using their time with me to focus more on technique and skill and try to keep in mind that I'm training for competition too!