Generally speaking, great people realize that they didn't achieve their success on their own. There were many people behind the scenes, helping, encouraging, etc. They realize that it was a team effort to be successful.
The not-so-great people are usually envious of others which inhibits success. When you open your hand, you can receive your blessings. When you close it tight to hang onto things, you're not in a position to be receptive, to be open to what the world has to offer.