It can help to know about one of the Buddha's top disciples, Mogallana, or Maha Mogallana as he's called. The Buddha had two top disciples - Mogallana and Sariputta. Sariputta had the highest wisdom of all the disciples. Mogallana had the highest psychic powers, plus he had super-wisdom, too, although not as high as Sariputta's. These were the two top disciples of the Buddha. They were the two most important people on the whole planet beside the Buddha at that time.
Now when you think of human potential, it may be helpful to know what the scriptures say about Mogallana's past lives. Because when you are thinking of who you are now and you think you don't have potential, it's helpful to compare yourself to him. First I'll mention that in his last life even though he was enlightened, super-gifted and he had all the psychic powers, he was murdered. A person with psychic powers getting murdered, it doesn't work, right? It did for Mogallana.
For just for a few moments he lost his powers so that he was beaten up and left for dead. Then the powers came straight back. Beaten up, dying, hhe floated to the Buddha and said goodbye before he died. His powers left him for a short time. Why did they leave this super-gifted person? Because way, way back, 500 or 1000 lifetimes before, he killed both his mother and father in the same lifetime. As a Kammic result of that action, every single lifetime after that he was murdered. It didn't matter even though he was a great enlightened person full of compassion and love, he had never done anything wrong in his particular lifetime, but he still had to suffer the Kammic result of murdering his mother and father. Not only that, but in the lifetime when he murdered both of them, the Kammic result for that was rebirth in the bottom hell and to stay in there for eons and eons, so he suffered.
Now, do you rank with that? I don't think so. So compare yourself to Mogallana, this guy was one of the greatest human beings in his last life, but way, way back he was far below you on human potential level.
It is also helpful to know that after he stayed in hell for eons, he slowly evolved, getting reborn, as the chain goes, to the animal realms and so on. And when he was reborn as a human he was stupid again. During the time when a different Buddha was alive, Mogallana got angry at an enlightened disciple. He threw a rock which hit the disciple on the head and made him bleed. Kammic result for that? Can you guess? Down again. Ok, yet in his final life time he was a super-gifted person, so way back then when he was a stupid idiot throwing a rock at an enlightened person and even more than that back when killed his mother and his father, his potential you could say was so low you would have though he had no chance. But he made it!
With the thought that you don't have the same sort of potential as other enlightened people, forget it! It's there, ok? Have you grown in any way, have any single one of you grown in any way since you started your mental development practice? I would have to think the answer is yes. Right?
Now, logically speaking, from today to back when you started, for some of you it's about twelve years, for some of you it's a couple of years, from today going back to where you started, you've grown, haven't you? Now, why did you grow? You put in proper causes for growth. You did your practice, you tried to be loving at home, etc. You put in causes so you grew from that point to today. Now, if you put in more causes, what's going to happen? You'll have to grow some more, right? It's just A+B=C. You keep putting in the A and B.