Quoting from another site:
THE STORY OF THE CRAB BUCKET
One time a man was walking along the beach and say another man fishing in the surf with a bait bucket beside him. As he drew closer, he saw that the bait bucket had no lid and had live crabs inside.
"Why don't you cover your bait bucket so the crabs won't escape?", he said.
"You don't understand.", the man replied, "If there is one crab in the bucket it would surely crawl out very quickly. However, when there are many crabs in the bucket, if one tries to crawl up the side, the others grab hold of it and pull it back down so that it will share the same fate as the rest of them."
So it is with people. If one tries to do something different, get better grades, improve herself, escape her environment, or dream big dreams, other people will try to drag her back down to share their fate.
We have been enriched by the talents of people who have had less than "perfect" bodies, whether by birth, accident or disease - Helen Keller, F.D. Roosevelt, Stephen Hawking, George Bush, Stevie Wonder, Christopher Reeve, to name just a few.
They chose to "climb the crab bucket" instead of listening to others.