You can't have everything. Don't get jealous of what others have. Instead of letting yourself get jealous and frustrated, accept what you can't have. Turn it into a positive: reflect long and hard and and you'll learn to appreciate what you do have and what you'll work towards for the future. After all, it's not the people who have lots of money and possessions who are the happiest!
Jealousy and envy will only lead to tension with others, so hold yourself back from envy and be positive about what you have.