Some people attain what they want by applying hard work and lots of breaks and others have breaks handed to them on a silver platter. Some people that haven't had the money or chances to better themselves may become jaded and appear ungrateful and jealous of others. Some people just can't be happy for someone they know be it family or a friend that has a good piece of luck coming their way. They feel it should be them. Most people who feel ungrateful or jealous have no self confidence. If they did they wouldn't be wasting their energy on these two topics. If we work hard we all achieve goals although it may not be the goals we wanted, but you take what you can and run with it.
Some who are confident can be Jealous, they may see others in a different light for a wide range of reasons. How they were raised and or environment they had been subject to could account for their basis of actions or opinion. They may make statements that are half truth or out right demeaning, by doing so feel they have some how looked smart enough to see, know and have intelligent insight about others. Makes me think of a insecure person that feels they are loosing others respect or status, that there maybe a changing of the guards or may not be seen to be what they once were or no longer the leader or not the favorite. This shows each case is unique and may be interpreted in many ways which tells us you or others can be confident and still be jealous.