Compassion is the way to not feel superior. Remembering when we have also seen similar qualities arising in ourselves and that we are not yet enlightened, this helps to bring up a certain amount of humbleness. The realization, that we are still attacked by the hindrances from time to time, that we are not yet fully free from greed, hatred and ignorance, helps us see that it's not wise to judge another person's potential.
It is good to reflect that we have been so fortunate to have met with the Buddha Dhamma, even more fortunate to understand the Buddha Dhamma and especially fortunate to meet others who are practicing and teaching who can guide us. Then by remembering how our practice came to be, remembering that it depended on millions of people throughout the centuries right back to the Buddha helps to let go of a feeling of conceit. That any understanding that arises due to our practice was also dependent on others and in that way we try not to limit another person's potential.
When I first started practicing, I was pretty messed up and there was a good chance that my first teacher would have thought that I did not have much potential. If she had acted in that way, she may not have bothered giving me much time. However she didn't and later in her life we were corresponding with each other quite a lot, and I think that she was quite happy to see the results of my practice.
So we try not to limit another person's potential. You never know what experience in life may ignite their past Kamma.