A friend once explained something to me that illustrates this concept very well. He told me that as people catch crabs, they'll toss the crustaceans into a basket. If you have only one crab in the basket you need a lid to keep it from crawling out, but if you've got two or more, you don't. When there are several crabs, they will drag one another down so that none of them can get away.
A lot of unsuccessful people act the same way. They'll do things to keep others from getting ahead. But the good news is that if you observe someone trying to do that, you don't have to buy into their belief system. You can get out and stay out of the basket by refusing to be a crab.